Question

The average of 6 number is 30 if the average of first 4 is 25 and that of the last 3 is 35 then find the 4th number

Answer 1

in this problem

6 number average = 30

6 × 30 = 180 sum

but

first 4 number average is 25

4 × 25 = 100 sum

and last 3 is

3 × 35 = 105

sum = 100 + 105 = 205

4th number = 205 - 180 = 25