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Old 19th November 2014, 11:26 AM
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Join Date: Apr 2013
Default Re: Tips and Tricks to Solve Quantitative Aptitude Test Questions

Here I am suggesting few Tips and Tricks to Solve Quantitative Aptitude Test Questions on Number System which you are looking for .

Formulas of Number Series
1 + 2 + 3 + 4 + 5 + … + n = n(n + 1)/2
(12 + 22 + 32 + ..... + n2) = n ( n + 1 ) (2n + 1) / 6
(13 + 23 + 33 + ..... + n3) = (n(n + 1)/ 2)2
Sum of first n odd numbers = n2
Sum of first n even numbers = n (n + 1)


Mathematical Formulas
(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
(a + b)n = an + (nC1)an-1b + (nC2)an-2b2 + … + (nCn-1)abn-1 + bn

Shortcuts for number divisibility check
A number is divisible by 2, if its unit's digit is any of 0, 2, 4, 6, 8.
A number is divisible by 3, if the sum of its digits is divisible by 3.
A number is divisible by 4, if the number formed by the last two digits is divisible by 4.
A number is divisible by 5, if its unit's digit is either 0 or 5.
A number is divisible by 6, if it is divisible by both 2 and 3.
A number is divisible by 8, if the number formed by the last three digits of the given number is divisible by 8.
A number is divisible by 9, if the sum of its digits is divisible by 9.
A number is divisible by 10, if it ends with 0.
A number is divisible by 11, if the difference of the sum of its digits at odd places and the sum of its digits at even places, is either 0 or a number divisible by 11.
A number is divisible by 12, if it is divisible by both 4 and 3.
A number is divisible by 14, if it is divisible by 2 as well as 7.
Two numbers are said to be co-primes if their H.C.F. is 1. To find if a number, say y is divisible by x, find m and n such that m * n = x and m and n are co-prime numbers. If y is divisible by both m and n then it is divisible by x.

List of few questions are given below
Given a number x, you will be asked to find the largest n digit number divisible by x.

Given a number series, find the sum of n terms, find nth term etc.

Find the number when divisibility of its digits with certain numbers is given.
Find the smallest n digit number divisible by x.

Find product of two numbers when their sum/difference and sum of their squares is given.

Which of the given numbers are prime numbers.

Number x when divided by y gives remainder r, what will be the remainder when x2 is divided by y.

Given relationship between the digits of number, find the number.
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