GATE 2020 ST – Question 5
General Aptitude · Quantitative Aptitude: Algebra, Geometry and Mensuration · 1 mark · Multiple choice
Subtract the sum of the first n odd positive integers from the sum of the first2n positive integers.
- $n^2-n$
- $n^2+n$
- $2n^2-n$
- $2n^2+n$
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Show answer and explanation
Correct answer: (B) $n^2+n$
Explanation
The first2n natural numbers sum to(2n)(2n+1)/2=n(2n+1). The first n odd numbers sum to n². Difference=2n²+n−n²=n²+n, B.
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