Ms. Shakuntla asked his students to find the sum of all pages of their maths book. Pappu gave the an

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04 Sep 2020 Arithmetic

Ms. Shakuntla asked his students to find the sum of all pages of their maths book. Pappu gave the answer as 1098. Ms. Shakuntla told him that he has not added one page.
Find the page number which the Pappu forgot to add?

OPtion

1) 27
2) 19
3) 33
4) 39
5) 38
6) 45
7) 30
8) 41
9) 43
10) None of these

Solution

1 + 2 + 3 + .........+n = 1098
⇒ n(n+1)/2 = 1098
⇒ n(n + 1) = 2196
⇒ n^2 = 2196.
Now, the perfect square closest 2196 is 2209, which is the square of 47.

Sum will be -
47*48/2 = 1128

As the given sum is 1128, so the Pappu forgot to add page number 1128 - 1098 = 30

Correct Option: 7 Best Solution (3)