UPSC CSE Prelims 2020
Let the booklet have pages. Pages are numbered starting from 1. The total sum of all page numbers is given by the formula: Sum.
The sum of the numbers on the remaining pages is 195.
To determine the total number of pages () in the booklet, we identify the smallest for which the total sum of page numbers is greater than 195, as one page was torn.
The original calculation demonstrates: .
This implies that the sum of the numbers on the torn page is 15.
Since a torn page always contains two consecutive page numbers, we must identify two consecutive integers that sum to 15. These numbers are 7 and 8 ().
Therefore, the torn page contains the numbers 7 and 8.
Option (A) 5, 6: The sum of these numbers is \(5 + 6 = 11\). This does not match the calculated sum of 15 for the torn page.
Option (C) 9, 10: The sum of these numbers is \(9 + 10 = 19\). This does not match the calculated sum of 15 for the torn page.
Option (D) 11, 12: The sum of these numbers is \(11 + 12 = 23\). This does not match the calculated sum of 15 for the torn page.