Mitu is 60 years old and Ritu is 80 years old. How many years ago their age ratio was 4 : 6?

Question: Mitu is 60 years old and Ritu is 80 years old. How many years ago their age ratio was 4 : 6?

Solution:
Let us assume x years ago.
At present, Mitu is 60 years old
and Ritu is 80 years old.
X years ago, Mitu’s age = (60 - x) and Ritu’s age (80 - x)

ATQ,
(60 - x)/(80-x) = 4/6
⇒ 6(60 - x) = 4(80 - x)
⇒ 360 - 6x = 320 - 4x
⇒ 6x - 4x = 360 - 320
⇒ 2x = 40
∴ x = 20

Therefore, 20 years ago their age ratio was 4 : 6.