Question

the average age of sons and their father is 20 years. If the average age of sons is 10 years, find the age of their father?

Answer 1

Solution:
 
Given: The average age of sons and their father is 20 years.
            The average age of sons is 10 years ,.

let the father's age be x

so, average of the age of father and his sons = 20
                                                               (x+10)/2 = 20
                                                                     x+10 = 20×2
                                                                     x+10 = 40
                                                                            x = 40-10
                                                                            x = 30
                        ∴ the age of father is 30