The ratio of the age of a man and his wife is 4:3. At the time of marriage the ratio was 5:3 and After 4 years this ratio will become 9:7. How many years ago were they married?
Let the present age of the man and his wife be 4$x$ and 3$x$ respectively.
After 4 years this ratio will become 9 : 7
=> $\left(4x + 4\right)$ : $\left(3x + 4\right)$ = 9 : 7
=> 7$\left(4x + 4\right)$ = 9$\left(3x + 4\right)$
=> 28$x$ + 28 = 27$x$ + 36
=> $x$ = 8
Present age of the man = 4$x$ = 4×8 = 32
Present age of his wife = 3$x$ = 3×8 = 24
Assume that they got married before t years. Then
(32 - t) : (24 - t) = 5 : 3
3(32 - t) = 5(24 - t)
=> 96 - 3t = 120 - 5t
=> 2t = 24
=> t = $\dfrac{24}{2}$ = 12