Ten years ago, A’s mother was four times as old as A. After ten years she will be twice as old as A. Find the present age of A.

20 years

Let the age of mother 10 years ago = 4R,

then age of A 10 years ago = 1R

ATQ,

⇒ \(\frac{4R\;+\;20}{1R\;+\;20}\) = \(\frac{2}{1}\)

⇒ 4R + 20 = 2R + 40

⇒ 2R = 20

⇒ 1R = 10

Age of A at present = 10 + 10 = 20 years