Question

Out of eight numbers, the sum of first seven numbers is 8 times the 8th number. If their average is 153, then the 8th number is:​

Answer 1

Given - Total numbers = 8

Sum of first seven number = 8 times the 8th number.

Average of the numbers = 153.

Find - The 8th number.

Solution - Average = sum of all the numbers/total numbers.

Let the 8th number be X.

Sum of seven numbers = 8*X = 8x.

Average of all 8 numbers = sum of all seven number + 8th number /8

Average = 8x + x/8

153 = 9x/8

9x = 153*8

9x = 1224

X = 136.

Hence, the 8th number is 136.