SUM RULES
SUM RULES
Sum Rules
Here we’ll be discussing the basic formulas of Arithmetic Progression and Geometrical Progression.
Arithmetic Progression
If An A.P. with first term a and common difference d is given as-
a, (a+d), (a+2d), (a+3d), ….. a, (a+d), (a+2d), (a+3d) ,…..
Then the formula to calculate its nth term will be –
Tn = a + (n−1) * d.
The sum of n terms of this A.P.
Sn = (n2) * [2a +(n − 1) * d]
Sn = (n2) ∗ (first term + last term).
Also practice with -
(1+2+3+………+n) = ½ * n * (n+1)
(12+22+32+………+n2) = 1/6 * n * (n+1) * (2n+1)
(13+23+33+………+n3) = 1/4 * n2 * (n+1) * 2.
Geometric Progression
A G.P. with first term a and common ratio r is –
a, ar, ar2, ….. : a, ar, ar2, …..
In this G.P. nth term =
Tn = a*r(n−1)
Sum of n terms=
Sn = a * (1−rn) / (1−r)
Sn = a * (1−rn) / (1−r); when r>1.
Number System Formulas – Learn the Basics!
Sample Maths Number System Questions – FAQ’s!
Type-1: Given a number x, you will be asked to find the largest n digit number divisible by x.
Type-2: You will be given with a set of numbers (n1, n2, n3…) and asked to find how many of those numbers are divisible by a specified number x.
Type-3: Given a number series, find the sum of n terms, find nth term etc.
Type-4: Find product of two numbers when their sum/difference and sum of their squares is given.
Type-5: Find the number when divisibility of its digits with certain numbers is given.
Type-6: Find the smallest n digit number divisible by x.
Type-7: Which of the given numbers are prime numbers.
Type-8: Number x when divided by y gives remainder r, what will be the remainder when x2 is divided by y.
Type-9: Given relationship between the digits of number, find the number.
Type-10: Find result of operations (additions, subtractions, multiplications, divisions etc.) on given integers. These integers can be large and the question may look difficult and time consuming. But mostly the question will map onto one of the known algebraic equations given in this first tab.
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