The ratio of the present ages of P and Q is 3 : 4. Five years ago, the ratio of their ages was 5 : 7. Determine how old Q is right now.

Question: The ratio of the present ages of P and Q is 3 : 4. Five years ago, the ratio of their ages was 5 : 7. Determine how old Q is right now.

Solution:
As the ratio of their present ages is 3 : 4 ,

let,
their present ages be 3X and 4X.
So, 5 years ago, as the ratio of their ages was = 5 : 7,

we can write,
(3x - 5) : (4x - 5) = 5 : 7
⇒ (3x - 5)/(4x - 5) = 5/7
⇒ 21x - 35 = 20x - 25
⇒ x = 10

∴ their present age of Q = 4X = 40