Question

There is a list of seven numbers. The average of the first four numbers is 5, and the average of the last four numbers is 8. If the average of all seven numbers is (6 + 4/7), find the number common to both sets of four numbers.

Answer 1

6

Explanation:

Sum of first 4 numbers= 4*5= 20

This includes 3 + 4th number

Sum of last 4 numbers= 4*8= 32

This includes 4th number + 3

Sum of 7 numbers= 7*(6+4/7)= 46

This includes 3+4th number +3

Number common to both sets= (20+32)- 46 = 6