Question

The average of 8 numbers is 20. The average of first two numbers is 21 1 3 and that of next three is 1 15 2 . If the sixth number is less than the seventh and the eighth numbers by 4 and 7 respectively, then the eighth number is-

Answer 1

Answer:

Let the sixth no. = x

then the seventh = x + 4 and the eighth = x + 7

According to the question,

2×312+3×643+x+x+4+x+7=8×20

31 + 64 + 3x + 11 = 160

106 + 3x = 160

3x = 54

x = 18

∴ Eighth no. x + 7 = 18 + 7 = 25