Question

The average of eight numbers is 20. The average of first two numbers are 15.5 and that of the next 3 is 211/3. If the 6th number is smaller than 7th and 8th numbers by 4 and 7 respectively, then find the 7th number.

• A. 18
• B. 22
• C. 25
• D. 27

Answer 1

The correct option is B 22

Sum of all the numbers $=\frac{8}{20}=160$
Sum of last 3 numbers $=160-(2\times 15.5)-(3\times 21\frac{1}{3})=65$
If 6th number is x, then 7th and 8th numbers are x+4 and x+7
Then, x+ x+ 4+ x+ 7 = 3x+11 = 65
Therefore required answer is x+4 = 22