Variance

Variance Variance (σ2) in statistics is a measurement of the spread between numbers in a data set. That is, it measures how far each number in the set is from the mean and therefore from every other number in the set. In investing, the variance of the returns among assets in a portfolio is analyzed … Read more

Number System

 Number system 1. Basic Formulae  (a + b)(a – b) = (a2 – b2) (a + b)2 = (a2 + b2 + 2ab) (a – b)2 = (a2 + b2 – 2ab) (a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ca) (a3 + b3) = (a + b)(a2 – ab + b2) (a3 – b3) = (a – b)(a2 + ab + b2) (a3 + b3 + c3 – 3abc) = (a + b + c)(a2 + b2 + c2 – ab – bc – ac) When a + b + c = 0, then a3 + b3 + c3 = 3abc   2. Types of Numbers I. Natural Numbers Counting numbers 1,2,3,4,5,…1,2,3,4,5,… are called natural numbers   … Read more

Time & Work

 TIME AND WORK In these problems the number of persons, quantity of work done and time taken are important factors. Also time taken by a person depends on the efficiency of that person which comes into picture when different people do the work such as Women, children do the work … Read more

Surds And Indices

     SURDS A surd is a square root which cannot be reduced to a rational number. For example,  is not a surd. However  is a surd. If you use a calculator, you will see that  and we will need to round the answer correct to a few decimal places. This makes it less accurate. If … Read more

Simple Interest

 MATHEMATICS AND QUATITUATIVE Aptitude – SIMPLE INTEREST Introduction Money is not free and it costs to borrow the money. Normally, the borrower has to pay an extra amount in addition to the amount he had borrowed. i.e, to repay the loan, the borrower has to pay the sum borrowed and the interest. Lender … Read more

Puzzle Test

 Puzzle test Puzzle Test section comprises problems put in the form of puzzles involving certain number of items, be it persons or things. The candidate is required to analyse the given information, condense it in a suitable form and answer the questions asked.     In this type of test, the questions are … Read more

Pipe And Cistern

 Pipes and Cistern   Inlet: A pipe connected with a tank or a cistern or a reservoir, that fills it, is known as an inlet.   Outlet: A pipe connected with a tank or cistern or reservoir, emptying it, is known as an outlet.   If a pipe can fill a tank in x hours, … Read more

Percentage

          Important Formulas – Percentage Percentage Percent means for every 100 So, when percent is calculated for any value, it means that we calculate the value for every 100 of the reference value. percent is denoted by the symbol %. For example, x percent is denoted by x% x%=x/100 Example : … Read more

Median

 Median Median is the middle number in a sorted list of numbers. To determine the median value in a sequence of numbers, the numbers must first be arranged in value order from lowest to highest. If there is an odd amount of numbers, the median value is the number that is in the … Read more

Hcf And Lcm

  HCF & LCM HCF & LCM are acronym for words, Highest common factor and Lowest common multiple respectively. 1. H. C. F While we all know what a multiplication is like 2 * 3 = 6. HCF is just the reverse of multiplication which is known as Factorization. Now factorization is breaking … Read more

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