Question

The average age of 3 boys is 12 years the average age of 2 of them is 13 years find the age of the third boy

Answer 1

Answer:

let age of 1st boy be x

age of 2nd boy be y

age of 3rd boy be z

average age of 3 boys = 12 years

ATQ

(x + y + z)/3 = 12 yrs

x + y + z = 36 yrs

means sum of all the ages is 36 yrs.

now

average age of two of them is 13 years

(x + y)/2 = 13

x + y = 26 yrs

sum of age of two of them is 26 years.

age of 3rd boy i.e. (z) = sum of all age - sum of age of two boys

= x + y + z - (x+y)

put their values

age of 3rd boy = 36 - 26 = 10 yrs

so the age of 3rd boy is 10 years.

hope this will help you