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

RRB NTPC · Question 17

The difference between the mean of the first eight composite natural numbers and the mean of the first eight prime numbers, is:

  1. 1/4

  2. 3/20

  3. 1/5

  4. 1/8

Show answer & explanation

Answer: (D) 1/8

Explanation

First eight composites: 4, 6, 8, 9, 10, 12, 14, 15 – sum 78, mean 9.75. First eight primes: 2, 3, 5, 7, 11, 13, 17, 19 – sum 77, mean 9.625. Difference = 0.125 = 1/8.