Discussion of Question with ID = 048 under Averages

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Question

What is the average of first 275 natural numbers?

A

138.

B

139.

C

137.

D

136.

Soln.
Ans: a

The sum of first n natural numbers is $(n × (n + 1))/2$. The average is ${(n × (n + 1))/2}/n$ which is $(n + 1)/2.$ Putting n = 275, we get average = 138.


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