The ratio between the present age of P and Q is 6 : 7. if Q is 4 years old then P, what will be the ratio of the ages of P and Q after 4 year ?  Choose the correct answer.
A) 3 : 4
B) 3 : 5
C) 7 : 8
D) 4 : 3
E) None of these
Solution   Let P's age and Q's age be 6x years and 7x years respectively.   Then, 7x - 6x = 4 ⇔ x = 4.   ∴ Required ratio = (6 x + 4) : (7 x + 4) = 28 : 32 = 7 : 8 .Answer 7 : 8
<result>C</result>
The ratio between the present age of P and Q is 6 : 7. if Q is 4 years old then P, what will be the ratio of the ages of P and Q after 4 year ?