Single correct option
The present ages of P and Q are in the ratio 5 : 7. Eight years from now the ratio will be 7 : 9. What is the sum of their present ages (in years)?
- A. 40
- B. 48
- C. 56
- D. 60
Show answer and solution
Answer: (B) 48
Let the ages be 5x and 7x. Then (5x + 8)/(7x + 8) = 7/9.
Cross-multiplying: 45x + 72 = 49x + 56, so 4x = 16 and x = 4.
The ages are 20 and 28, and the sum is 48.
Tip: the difference in ages never changes. It is 2 parts now and 2 parts later, so each part is the same size (4) and 2 extra parts = 8 years. Now = 12 parts = 48.
Cross-multiplying: 45x + 72 = 49x + 56, so 4x = 16 and x = 4.
The ages are 20 and 28, and the sum is 48.
Tip: the difference in ages never changes. It is 2 parts now and 2 parts later, so each part is the same size (4) and 2 extra parts = 8 years. Now = 12 parts = 48.
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