eChapters

A ratio is the comparison or simplified form of two quantities of the same kind. This relation indicates how many times one quantity is equal to the other; or in other words, ratio is a number, which expresses one quantity as a fraction of the other. For example, the ratio of 1 to 2 is 1 : 2. The numbers forming the ratio are called terms. The numerator, “1”, in this case, is known as the antecedent and the denominator, “2”, in this case, is known as the consequent.

In this article we will learn the approach applicable to solve various problems on ratios and proportions. In the next few lines you will go through some important concepts related to ratio problems and the methods you should apply to solve those problems. It is always better to solve as many problems as you can to boost your confidence. Some important points are given below to remember;

A pipe is connected to a tank or cistern. It is used to fill (inlet) or empty (outlet) the tank. Therefore, Inlet refers to a pipe which is connected to fill a tank is known as an inlet, while outlet refeRs to a pipe which is connected to empty a tank is known as an outlet. Generally the problems on pipes and cisterns are similar to problems on time and work. In pipes and cistern problems, the amount of work done is the part of the tank of filled or emptied. And, the time taken to do a piece of work is the time taken to fill or empty a tank completely or to a desired level. Following points should be remembered to solve the probles;

The area of circle, rectangular, square, triangle, trapezium, rhombus,parallelogram etc are to be calculated by simple formulae but some times the combined area of more than two either circles or trapezium is difficult to calculate. It needs to understand the concept of area and how it is related to different planes. Some of the tips are given below to understand how to calculate the are

a. Area

A part of the plane enclosed by a simple closed figure is called a plane region and the measurement of plane region enclosed is called its area. Area is measured in square units.

The different geometrical shapes formula of area and perimeter with examples are discussed below:

Introduction

It is a very important chapter as many questions are asked in competitive examination based on time and work relationship. This topic deals with the simultaneous performance involving the efficiency of an individual or a group and the time taken by them to complete a piece of work. Work is the effort applied to produce a deliverable or accomplish a task. A certain amount of time (T) is taken to complete a certain work (w). The number of units of work done per unit time is called the rate of work (R).

Hence, Work (W) = R x T

Whenever some work is done, the total work itself can be taken as one unit. Hence, we assume the total work done as one unit in the problems we encounter in order to simplify the computations. In these cases, R = 1 / T or T = 1 / R. In other words, R and T are inversely proportional as R T = W, which is a fixed quantity.

Aptitude questions related to ages are commonly asked in various competitive exams, so you should definitely solve few questions for exercise. Now let us go through the different types of statements used in this topic.

Let us find the age of Rakesh by understanding his statement. Let us take the kid’s current age as X. So as per statement given by him, X = 1.5(X – 10). Solving for X, we get the value of X as 30. Hence current age of Rakesh’s son is 30 years.

What is an Average ?

The word “average” is used in everyday life to describe where the middle number of a data set is. It’s the typical number you would except to find in a series of numbers. In statistics, the average is called the “arithmetic mean” usually just shortened to the mean. Both the average and the mean use the same formula :

Avg = total sum of all the numbers/ number of items in the set.

In other word, to find the average, add up all of the numbers in the set, and then divide by however many items you have. Let’s say you have 5, 10, and 15. Add them all up to get 5 + 10 + 15 = 30, then divide by 3(the number of items). The answer is 30/3 = 10.

In probability and statistics, you’ll see the following formula used

The numerical based on simple mathematics like divide, multiply, sum, deduction, under root, percentage etc are given below to sharpen the inherent ability of the students. This simplication is a very good exercise to aqcquaint the students about basic mathmetics so that they can solve tough questions quickly. Therefore some tips are given below for solving the questions.

[Schoonover (1952) Method]

Introduction

Sodic (Alkali) and Saline-Sodic soils are characterized by the presence of large amounts of sodium, as high as 15% or more, on their exchange complex. As a result of this, the pH of soils increases beyond 8.0, causing nutritional imbalances, elimination of soil organic matter, deterioration of soil physical condition, etc., besides affecting the soil biotic community. Gypsum (CaSO₄. 2H₂O) is commonly used for the management of such soils, when applied in right amounts and size.

Principle

A given weight of soil is equilibrated with a known amount of Ca solution, and the amount of Ca, left in the solution is determined by EDTA titration. The difference between the amount of Ca added and the Ca left in the solution, gives the amount of Ca exchanged. In practice, gypsum of about 1/3 of the value, obtained by this method, is satisfactory in most cases.

[Shoemaker, Mc Lean and Pratt (SMP) Method, 1961]

Introduction

For proper plant growth, the soil should have a pH between 6.5 and 7.5, though there are certain plants which can grow satisfactorily at low pH, for example, tea, and at high pH, for example, sugar beet. In India, acid soils are located mostly in Eastern, Southern and South Central parts though some soils, at higher elevations, in North India are acidic.

In order to achieve maximum yield and sustained productivity through efficient soil management practices, it is essential to lime an acid soil, as it has considerable influence on soil environment, besides correcting soil acidity.

Several methods have been proposed to determine the lime requirement of acidic soils, to raise the pH around 6.5. The soil pH value alone, however, is not a good criterion for lime recommendation, because of variations in the exchange acidity of soil, and the nature of crops which may not require as high as this pH to produce maximum yield. Of these various methods proposed, the Shoemaker / SMP method was found satisfactory.

The recent trend of liming is to use it as a fertilizer rather than as amendment so as not to disturb heavily the natural environment while ensuring sustained productivity.

[Williams and Steinbergs (1959) Method]

Introduction

Sulphur (S) occurs in numerous forms in soil, viz., sulphites, sulphates, sulphides and in organic compounds. It is considered that the most accessible form is ‘sulphate’ (SO₄ ^2–). The organic forms of S compounds become assimilable, especially following, microbiological transformation into SO₄ ^2–. The mineralization of organic S in a soil depends primarily upon the N:S ratio, and any SO₄ ^2– formed may be fixed against extraction, particularly if much Fe or Ba is present or if the soil is very acid. Despite the fact that the plants absorb S almost exclusively as SO₄ ^2–, mobility of SO₄ ^2– in soil may not always yield satisfactory results in accordance with the time of sampling, while assessing SO₄ ^2– availability.

(Neutral Normal Ammonium Acetate Method)

Introduction

The total potassium (K) content of a soil varies from 0.05 to 2.5 %. The total K is distributed in mineral form (lattice – K, 90-98 %), fixed non-exchangeable or temporarily retrograded K (1-10 %) and exchangeable plus water soluble K (1-2 %). Exchangeable K represents an average of 2 – 15 % of the sum of exchangeable bases and 1 – 3 % of the total capacity for cation exchange. The K concentration in the soil solution is on an average 0.08 – 3 meq/litre. Both water soluble and exchangeable K are most accessible to the plant. Available K can, thus be separated into that, immediately available, which is water soluble and exchangeable, and that, potentially available or fixed. The neutral normal ammonium acetate extract contains both water soluble and exchangeable K. K extraction by this extractant is considered as a suitable index of K availability in most soils, based on crop response correlation study. Thus, the K extracted by this method is equated as the available K.

[Bray’s Method (Bray and Kurtz, 1945) – Acid Soils]

Introduction

The term available phosphorus (P) refers to the inorganic form, occurring in the soil solution, which is almost exclusively ‘orthophosphate’. This orthophosphate occurs in several forms and combinations, and only a small fraction of the total amount present may be available to plants, which is of direct relevance in assessing the P fertility level.

The phosphate concentration in solution is governed by heterogeneous equilibria in which it takes part. This situation can be represented as follows:

P adsorbed in solid phase ↔ P in the soil solution ↔ P precipitated

The phosphorus absorbed by plants from soil solution comes from the soil solution in which it exists as inorganic orthophosphate ions viz., H₂PO₄ ^–, HPO₄ ^2– and PO₄ ^3–. The most accessible ion is H₂PO₄ ^–, with the greatest activity coefficient, followed by HPO₄ ^2–. The quantity of P accessible to the plants is influenced by a series of soil properties. The relative abundance of these ions is, however, relatively dependent on the soil pH. For soils having a pH between 4.5 and 7.5, ions of H₂PO₄ ^– as well as HPO₄ ^2– exist in soil solution. At a pH of 7.2, H₂PO₄ ^–and HPO₄ ^2– ions have an equal activity, and, when the pH is strongly alkaline (>8.3), ions of HPO₄ ^2– predominate in solution. Above pH of 9.0, the trivalent ion (PO₄ ^3–) becomes more important than H₂PO₄ ^–, but even at a pH of 12, the HPO₄ ^2– concentration is still greater than that of PO₄ ^3–. Soluble phosphorus may be adsorptively retained at the surface of colloidal particles. This retention is more marked when the higher amounts of clay and sesquioxides are present. Relatively, the available inorganic P tends to accumulate in its most stable state under prevailing conditions, thus, in calcareous soils, the available inorganic P would be acid-soluble, whereas, in acid soils the adsorbed P would be more available. In flooded soils, with low oxidation potential, certain forms of P, normally considered as unavailable, for example, iron and phosphate, can be regarded as available. In most soils, the main source of orthophosphate is organic matter unless, of course, direct fertilization, with soluble phosphate, has been made.

[Alkaline Permanganate / Subbiah and Asija (1956) Method]

Introduction

Nitrogen (N) is found in the arable horizon of the soil, mostly in organic material. In the soil solution, organic N is gradually transformed into ammoniacal (NH₄ ⁺), nitrite (NO₂ ^–) and nitrate (NO₃ ^–) nitrogen by microbial processes. Organic-N is, in itself, of very little use to plants, as it can not be absorbed as such. It is, therefore, necessary to estimate the different forms of mineralized or available N. The NO₃ ^–_N and NO₂ ^–-N together, hardly, exceed 1 % of the total N in normal soil.

The available N in soil refers to a fraction of the total N which is converted into forms accessible to the plants. This constitutes, on an average, only 0.5-2.5 % (rarely 5 %) of the total N in a soil at any given time. Nitrogen is, generally, absorbed by plants as NO₃ ^–, under oxidized environment (upland condition), and as NH₄ ⁺, under reduced condition. NO₂ ^– is sometimes, detectable, but the amount is, generally, very small vis-a-vis NH₄ ⁺ or NO₃ ^– and, hence does not warrant its determination. The sum total of NH₄ ⁺ and NO₃ ^–- N is smaller than the total N, which becomes available to plants and the difference being attributed to the mineralization of the organic N, during the crop growth cycle.

[Titrimetric/ Walkley and Black (1934) Method]

Introduction

The role of soil organic matter, in relation to soil fertility and physical conditions, are widely recognized. The organic matter is the source of plant nutrients which are released inassimilable forms during microbial degradation. A major proportion of N (95 – 99 % of the total), P (33 – 67 % of the total) and S (75 % of the total) in soils occur in organic combinations, which mineralize to release the nutrients in inorganic forms to be used by plants. Nevertheless, it serves as a reservoir of plant nutrients, in promoting water storage, and in regulating microbial activity.

The organic matter content of a soil varies from 0.344 % in very sandy arid soils to more than 86 % in Peats and Mucks. Soil organic matter contains 5 % N, and 0.5 % each of P and S, thereby, having a N:P:S ratio of 10:1:1. The organic matter content of a soil is estimated by the amount of organic carbon (C) present, as this element represents, on an average, 52 – 58 % of the organic matter, and the C:N ratio is 10 – 15. In the sub-soil, the average organic carbon amount is 36 – 44 % (40 %), and the C:N ratio is < 8. In order to find out the amount of humified organic material, the organic carbon content is multiplied by 1.724, which represents the ratio between the humus and the organic carbon (100/58) and is known as the ‘von Bemmlen factor ’.

The organic matter content of soils is estimated from the organic carbon, determined by using the ‘Titrimetric method / Walkley and Black method. The Titrimetric determination, also known as the ‘wet-digestion method’ involves a rapid titration procedure for the estimation of organic carbon content of soils.

The Electrical Conductivity (EC) of the soil is a measure of soluble salts present in the soil and is expressed as millimhos/cm or dSm^-1.

Principle

As the amount of the soluble salts in a solution increases, the electrical conductivity also increases. This electrical conductivity is measured in terms of resistance offered to the flow of current using a conductivity bridge.

It is known that solutions offer some resistance to the passage of current through them, depending upon the concentration of the soluble salts present. Hence, EC is measured in terms of electrical Resistance between parallel electrodes immersed in the soil water suspension.

In such a system, the solution between the electrodes becomes the electrical conductor to which the physical laws relating to resistance are applicable. The electrical resistance ‘R’ is directly proportional to the distance ‘L’ between the electrodes and inversely proportional to the cross sectional area ‘A’ of the conductor.

The pH is defined as negative logarithm of hydrogen ion concentration or the log of the reciprocal of the hydrogen ion concentration (Sorenson, 1906).

Principle

A glass electrode in contact with hydrogen ions of the solution acquires an electric potential which depends on the concentration of hydrogen ions. This is measured potentiometrically against some reference electrode which is usually a calomel electrode. The potential difference between glass electrode and calomel electrode is expressed in pH units.

Two electrodes are used in the determination of pH. One is reference electrode which provides a standard voltage and is usually a saturated calomel electrode which has two layers of saturated solution of KCl and mixture of solid HgCl₂ and Hg. The outer tube is usually 5-15 cm long, 0.5-1 cm in diameter. The mixture of solid HgCl₂ + Hg paste is contained in an inner tube that is connected to the saturated KCl solution in the outer tube by means of small opening. The resistance developed by this type of electrode is 2000-3000 Ohms.

The outer electrode is glass electrode that consists of a tube enclosing a lead wire made up of Ag coated with AgCl. This wire is again enclosed in a wax insulation. To the tube at the bottom is attached a glass bulb made up of a special kind of glass which is sensitive to hydrogen ions. The thickness of the glass membrane varies from 0.03 to 0.1 mm and has a resistance of 50 to 500 mega Ohms.

When these electrodes are dipped in solution, the saturated solution of KCl comes out of reference through small holes and forms an invisible ionic bridge between electrodes through which current passes. The hydrogen ions are absorbed by glass electrode and depending upon the amount of hydrogen ions present in the solution, an electric potential develops between electrodes. This potential difference is measured in terms of pH units by suitable Galvanometer.

(Keen-Rackzowski/Hilgard Apparatus Method)

Principle

With the capillary rise of water, the soil immediately above a water table gets saturated. The height upto which the soil is saturated depends on the texture, structure and packing of the soil mass. The experimental technique discussed herein permits approximation of maximum water holding capacity while determining the amount of water held in the soil at the point of saturation.

Principle

When water is ponded inside the concentric metallic rings driven into the soil, the rate of recession (fall) of the water level, or the rate of water withdrawn from a supply source used to maintain a constant head of water on the soil surface, gives the infiltration rate of the soil.

During infiltration of water into the soil, appreciable lateral movement of water may also occur. To avoid the error due to this lateral movement, two concentric rings are used. Equal heights of water are to be maintained in both the rings. The infiltration is measured in the inner ring only. The rate of water intake per unit area varies markedly with the size of the rings and the depth of the soil to which they are driven into. Infiltration rate studies are preceded by the profile, initial soil moisture and any other problems of the region in which the soil is located.

(International/Robinson’s Pipette Method)

Principle

This method is based on Stoke’s law. According to this law, the rate of fall of a particle in liquid is directly proportional to the square of its radius.

Bulk density is the mass per unit volume of soil including pore space. The normal range of bulk density in most soils is ranging from 1.02 to 1.80 g / cm³. The bulk density of coarse textured soils will be on the higher side while organic soils will have lower bulk density.

Particle density is the mass of soil per unit volume excluding pore space. Pore space is that fraction of soil volume not occupied by solid particles.

Principle

The bulk density and percent pore space are determined from the apparent and true volumes of the soil measures by adding a known quantity of water to a measuring cylinder contain a weighed quantity of soil.

Principle

Soil moisture content is determined by drying a known quantity of soil sample in an electric oven at 105° C to 110° C and finding out the loss in weight.

Soil is analyzed to know the nature of soil, to classify and advocate to farmers about the peculiarities of the soils and how much of fertilizers should be applied for better crop production.

A composite soil, of course, can not be moved to into a laboratory. The value of the laboratory work depends upon care in sampling. Each soil sample needs to be a fair representative of the specific area or horizon worth sampling.

If the sample is to be a representative of an area, it is necessary to take large number of samples spread over the area, pool them and sub-sample it so as to get a sample of desired size. For soil survey work, samples are collected from a profile which is typical of the soil of the surrounding area.

Principle

Equal volumes of all acids / bases containing their gram equivalent weights per litre of the solution react completely with each other.

More often, if the reagent is not a primary standard, a secondary standard solution must be prepared. The chemical is dissolved and made up or diluted to the desired concentration and then it is standardized against a primary standard or against another reliably known secondary standard solution. Such solutions are called as secondary standard solutions.

Principle

Standard solutions are the solutions of accurately known concentrations. There are two types of standard solutions viz., primary and secondary.

A known quantity of the substances is dissolved in a volumetric flask and the volume is made upto the mark. Standard solutions prepared in this way are known as primary standard. This method can be used for preparation of standard solutions of substances which satisfy the following conditions.

5.1 Volumetric Techniques or Titrimetric Analysis

Acid Base Neutralization Reactions-Acidimetry & Alkalimetry

Oxidation –Reduction Reactions-Oxidometry (Permanganometry) & Dichrometry

Practice to calculate the weight / volume of reagents required to prepare the following standard solutions.

Preparation of Standard Solution - (1 M, 0.1 M, 1 N, 0.1 N, 0.5 N, 5%, 10%, 20%, 10 ppm, 20 ppm, 100 ppm)

Instrumental methods of chemical analysis are the quantitative methods of analysis that use, as principal measuring devices, instruments other than those employed in conventional gravimetric and volumetric determinations.

The main basis for this method of analysis is the physical property of any particular element or compound being analyzed. These properties include:

2.1 Beakers

Beakers are the one of most important vessels used in laboratory which is made up of heat resistant glass.

They are available in various capacities ranging from 10 to 3000 mL.

For convenience of pouring solution, spout is provided in the beaker.

They are used to perform titrations & for boiling solutions, etc.,

Beakers are constructed in tall and low forms.

Analytical chemistry is a branch of chemistry dealing with the determination of constituents of a substance or mixture of substances.

1.1 Qualitative Analysis

Qualitative analysis deals with the identification of the constituents of a substance, mixture of substances, or solutions and the way in which component element or a group of elements are constituted.

1.2 Quantitative Analysis

Quantitative analysis is concerned with the determination of quantitative contents of individual element or group of elements or compound present in the substances. This branch of analytical chemistry is of enormous scope and importance in science, industry and agriculture. The quantitative analysis can be divided into several categories based on the different methods employed for their quantitative measurements such as:

12.1. Women in Agriculture

Women are actively involved in various agricultural activities.

11.1. Definition

Jones: Variations or modifications of any aspect of social process, social patterns, social interaction or social organization.

Gillin and Gillin: Variations from the accepted modes of life; whether due to alteration in geographical conditions, in cultural equipment, composition on the population or ideologies and whether brought about by diffusion or inventions within the group.

Davis and Mac Iver: Change in the relationships.

10.1. Social value

Ideas which help an individual to discriminate whether a particular object or behaviour is good or bad, desirable or undesirable.

Norms: Times rules which govern the action

Normative behavior: People are expected to behave in accordance with the values held by the individual.

S.C. Dood defined the value as “desiderata” i.e., anything desired or chosen by someone, sometime.

Value may be considered as attitude-related attribute that are projected upon people, objects and situations.

9.1. Rural Sociology

Science of rural society.

Study of sociological life in rural setting to discover their conditions and tendencies and to formulate principles of progress.

A.R. Desai: Rural Sociology involves the study of human relationships in rural situations.

8.1. Terms and definitions

8.1.1. Extension program

A written statement of situation, objectives, problems and solutions which has been prepared on the basis of an adequate and systematic planning effort and which forms the basis of extension teaching activities in a specific area for a given period.

7.1. Sriniketan Project (1914)

Shri Rabindra Nath Tagore in 1914 established a rural reconstruction institute at Sriniketan involving youth from a group of 8 villages.

Maintained a demonstration farm, a dairy and poultry unit, an outdoor clinic, a department of cottage industries and a village school.

Villages were expected to approach these agencies through village workers who lived in villages to obtain solution of their more pressing problems.

Scheme of land development and tree plantation were given due importance.

Experiment on paddy, sugarcane and cotton were undertaken.

6.1. Etawah Pilot Project (1948)

Started in 1948 by Mr. Albert Mayer of USA at Etawah district in UP

Funded by the Government of UP.

6.1.1. Objectives

To know the degree of productive and social improvements, through self confidence and cooperatives

To find how quickly these results could be attained

To know whether the results remain permanent even after the special pressure is withdrawn

To assess how far the results were reproductive in other places.

5.1. Diffusion

Process by which an innovation is communicated through certain channels over time among the members of a social system.

4.1. Information and Communication Technology

Refers to technologies that provide access to information through telecommunications.

Similar to IT, but focuses on communication technologies.

Includes the Internet, wireless network, cell phones, and other communication medium.

3.1. Communication

Leagans (1961) refers as process by which two or more people exchange ideas, facts, feelings or impressions in ways that each gains a common understanding of meaning, intent and use of messages.

Communis is Latin word - meaning common.

Act of getting a sender and a receiver tuned together for a particular message, or a series of message.

Winfield (1957) refers as whole learning process; encompasses

º Teacher - message or material to be taught

2.1. Radio

A popular communication medium

2.1.1. Historic features

In India, Madras Presidency Club pioneered radio broadcasting in 1924.

Due to financial difficulties, gave it up in 1927.

In 1927, businessmen in Bombay started Indian broadcasting Company with stations at Bombay and Calcutta.

But, failed in 1930.

1.1. Extension

Educational process for bringing about maximum number of desirable changes among the people

18.1. Buffer stock

Refers to stock of food grains maintained by government to be used as a buffer to cushion shocks of fluctuating supply and price, to meet the emergency needs and to meet the situations arising out of serious unexpected shortages resulting from transport bottlenecks, natural calamities like war, flood, famine, earthquakes, and from the influx of refugees.

17.1. Fruit Products Order (FPO), 1995

Promulgated under Section 3 of Essential Commodities Act, 1955.

For regulating sanitary and hygienic conditions in manufacture of fruit, vegetable products.

Mandatory for all manufacturers of fruit, vegetable products to obtain a license under this order.

16.1. World Trade Organization (WTO)

Only global international organization dealing with rules of trade between nations.

Location: Geneva, Switzerland

Established: 1 January 1995

Created by: Uruguay Round negotiations (1986-94)

Membership: 164 members representing 98% of world trade

Budget: 197 million Swiss Francs for 2018

Secretariat staff: 625

Head: Roberto Azevêdo (Director-General)

15.1. Minimum Support Price (MSP)

MSP are announced by GOI at beginning of sowing season for certain crops on basis of recommendations of CACP.

MSP is price fixed by GOI to protect producer - farmers against excessive fall in price during bumper production years.

Guarantee price for their produce from the Government.

Objectives are to support farmers from distress sales and to procure food grains for PDS.

14.1. Commission for Agricultural Costs and Prices (CACP)

Set up in January, 1965 in name of Agricultural Prices Commission (APC) on recommendations of Food grains Prices Committee headed by Shri L.K.Jha.

Prices for different agricultural crops by GOI on the recommendations of CACP are announced as minimum support prices, statutory minimum prices, procurement prices and issue prices.

13.1. Forms of business organisations

Factors to be given weightage for choice of a suitable form of organization

Type of business - service, trade, manufacturing.

Selection of industry and area of operation.

Scope of operations, volume of business and market size, including its expected growth potential.

Amount of capital funds required – initial capital, working capital.