Question

The average of three number 10,20,and24 is (10+20+4)/3=18. Now, the average age of three persons is 25years and their ages are in proportion 3:5:7. Find the age of youngest and oldest person.

Answer 1

Let the ages of the people be 3x, 5x, and 7x.

The average is 25

I.e., (3x+5x+7x)/3=25

15x/3=25

5x=25

x=5

So,

Youngest person = 3x = 3(5) = 15yrs

Middle person = 5x = 5(5) = 25yrs

Oldest person = 7x = 7(5) = 35yrs