GATE 2020 BM – Question 5

General Aptitude · Quantitative Aptitude: Data Interpretation, Arithmetic and Number Computation · 1 mark · Multiple choice

Find the difference between the sum of the first 2n natural numbers and the sum of the first n odd natural numbers.

$n^2-n$
$n^2+n$
$2n^2-n$
$2n^2+n$

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Show answer and explanation

Correct answer: (B) $n^2+n$

Explanation

The first 2n natural numbers sum to (2n)(2n+1)/2=2n²+n. The first n odd natural numbers sum to n². Subtracting gives n²+n, option B. Both sums start from the first positive member of their sequence.

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