Question

The mean of a set of seven numbers is 81. If one of the numbers is discarded, the mean of the remaining number is 78. The value of discarded number is

• A. 98
• B. 99
• C. 100
• D. 101

Answer 1

The correct option is B

99

Mean of 7 numbers = 81

$\therefore$ Total = 7 $\times$ 81 = 567

By discarding one number, the mean of the remaining 6 numbers = 78

$\therefore$ Total = 6 $\times$ 78 = 468

$\therefore$ Discarded number = 567 - 468 = 99