The age of the father 4 yr ago was 8 times the age of his son. At present, the father's age is 4 times that of his son. Find the present age of son.

Options

A. a. 9 yr
B. b. 7 yr
C. c. 14 yr
D. d. 18 yr

Answer

B

Explanation

Let present age of son = `x yr`
Then, present age of father = `4x yr`
Now, age of father 4 yr ago = `(4x - 4) yr `
Age of son 4 yr ago = `(x-4) yr `
According to the question
`(4x - 4) = 8 (x - 4) `
`implies 4x - 4 = 8x - 32`
`implies 4x = 32 - 4 = 28`
`therefore x = 28/4 = 7`
Hence, the present age of son is 7 yr.