The ratio between the ages of x and y at present is 3:4. Five years hence, the ratio of their ages will be 4:5; what is the present age of y in years ?
Let the present ages of x and y be 3a,4a respectively
After 5 years, their ages will be 3a+5 and 4a+5
$$\frac{3a+5}{4a+5} = \frac{4}{5}$$
==> 5(3a+5) = 4(4a+5)
==> 15a+25 = 16a+20
==> a=5
Present age of x = 3*5=15 years
Present age of y = 4*5=20 years
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