Mr. Ramanujam asked his students to find the sum of all pages of their maths book. Chatur gave the a

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22 Oct 2020 Arithmetic

Mr. Ramanujam asked his students to find the sum of all pages of their maths book. Chatur gave the answer as 8554.The teacher told him that he has not added one page.
Find the page number which the Chatur forgot to add?

OPtion

1) 72
2) 97
3) 92
4) 98
5) 89
6) 83
7) 81
8) 77
9) 79
10) None of these

Solution

1 + 2 + 3 + .........+n = 8554
⇒ n(n+1)/2 = 8554
⇒ n(n + 1) = 17108
Now, the perfect square closest 17108 is 17161, which is the square of 131.

Sum will be -
131*132/2 = 8646

As the given sum is 8646, so the Chatur forgot to add page number 8646 - 8554 = 92.

Correct Option: 3 Best Solution (3)