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Question
The sum of first n natural numbers is given by `1/2n^2 + 1/2n`. Find the sum of first 11 natural numbers.
Solution
Given, sum of first n natural numbers = `1/2n^2 + 1/2n`
Sum of first 11 natural numbers = `1/2(11)^2 + 1/2(11)` ......[Put n = 11]
= `1/2 xx 121 + 11/2`
= `121/2 + 11/2`
= `132/2`
= 66
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