Question

The average of 8 numbers is15. if the average of 7 of these numbers is 14, find the 8th number.

HOW DO YOU SOLVE IT??

Answer 1

average of 8 numbers = 15

now, sum of 8 numbers = S₁ = average of 8 numbers × 8 = 15 × 8 = 120

Now, average of 7 numbers = 14

so sum of 7 numbers = S₂ = average of 7 numbers × 7 = 14 × 7 = 98

So, eighth number = S₁ - S₂ = 120 - 98 = 22