CA Foundation · Quantitative Aptitude · Ratio and Proportion, Indices and Logarithms
The ratio of the ages of a father and son is 7 : 2. If componendo and dividendo is applied, the ratio (father + son) : (father − son) equals 9 : k. The value of k is:
The value of k is 5. With ages in ratio 7 : 2, the sum is 9 parts and the difference is 7 − 2 = 5 parts, so (father + son) : (father − son) is 9 : 5.
- A5Correct
- B2
- C7
- D4
Explanation
With ages 7m and 2m, the sum is 9m and the difference is 5m. So the ratio is 9 : 5 and k = 5. Option C wrongly uses 7, the father's share, instead of the difference 7 − 2.
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