NextMockSearch exams, e.g. SSC CGL, UPPSC, Lekhpal
Railways PYQCBT 1 2020

RRB NTPC · Question 9

In the following expression which number should be added so that it becomes a complete square? 1 + 3 + 7 + 9 + 11 + 13

  1. 5

  2. 7

  3. 3

  4. 1

Show answer & explanation

Answer: (A) 5

Explanation

The sum of the first n odd numbers is n². 1 + 3 + 7 + 9 + 11 + 13 is missing 5; adding it gives 49 = 7².