This question was previously asked in

MP Police Constable Previous Paper 21 (Held On: 31 Aug 2017 Shift 1)

Option 2 : 10 years

**Given:**

At present, Father's age = 4 × Son's age

After 20 years, Father's age = 2 × Son's age

**Calculation:**

Let the present ages of the Father and the Son be F and S respectively.

According to the question,

F = 4S ----(i)

Again, according to the question,

(F + 20) = 2 × (S + 20)

⇒ F + 20 = 2S + 40

⇒ F - 2S = 40 - 20

⇒ F - 2S = 20

Putting F = 4S from equation (i) in the above equation, we get,

(4S) - 2S = 20

⇒ 2S = 20

⇒ S = 20/2

⇒ S = 10 yrs

**∴ The present age of the Son is 10 years.**