Quantitative Reasoning

Thought to put together all formulas at one place:


Sum of all consecutive integers:

N (N+1) / 2 ------- (I)
where N is the number of terms.

Example: 1+2+3+........ + 100
N=100
(I) => 100 (101) / 2
=> 50 (101) = 5050

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SUM OF EVEN NUMBERS:

Formula: N(N+1)
How to Find N = (First Even + Last Even)/2 - 1

Example: 2+4+6+ ....... 100
N = (2+100)/2 - 1 = 50

Sum of first 50 positive even integers = (50)(51) = 2550
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SUM OF ODD NUMBERS:

If N = number of odd terms then sum = (N)^2