Bheja Fry question

 Question

The ratio between father and son age is 17 : 7.

6 years ago,  the ratio was 3  : 1.

What is the current age of father and son  ?? 

Answer

It is given that present age ratio of father and son is 17 :  7.

Let the age of father  17x

Age of son  7x

It is also given that 6 years ago, the ratio of their age was  7 :  1

Let the age 6 years ago, 

Father  17x  - 6

Son         7x  - 6

. 

Their age ratio  3 :  1

( 17 x  -  6 )  :  (  7 x  - 6  )  =   3 : 1

17 x  - 6              3

--------------     =   -----

7 x  -  6                1

Cross multiplying we get

17  x  -  6  =  3  (  7 x  -  6  ) 

17  x  -   6   =   21  x   -   18

21 x  -  17  x   =  - 6  + 18

4 x  =  12

X  =   3

At present, 

Son's age is   7 x  =  7  ×  3  =  21  years

Father's age is   17  x =  17  ×   3  =  51  years