Question

Average age of A, B and C is 10 years. If the average age of A and C is 9 years,
Then how many years old is B?

Answer 1

Answer:

Age of B is 12.

Step-by-step explanation:

Average age of A, B, and C = 10 years

( A + B + C) / 3 = 10

A + B + C = 30 ----- ( 1 )

Average age of A and C = 9 years

( A + C)/2 = 9

A + C = 18 ---- ( 2 )

Subtracting eq( 2 ) from eq( 1 )

A + B + C - ( A + C) = 30 - 18

A + B + C - A - C = 12

B = 12

Therefore the age of B is 12.

Answer 2

12 years

A+B+C/3 = 10 years

A+B+C = 30

A+C/2 = 9 years

A+C = 18 years

A+B+C-A+C = 30-18

30-18 = 12

Answer = 12 years

Hope it helps!!!