The ratio of ages of A and B is 7 : 5. Five years hence, the ratio will become 9 : 7. What percentage is the B to A?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 71.43%
B’s age as a percentage of A’s is \(\frac{\text{B}}{\text{A}}\times100\), and the present ratio 7 : 5 already gives this fraction.
Present ages: A \(=7x\), B \(=5x\)
B as a percentage of A \(\displaystyle=\frac{5x}{7x}\times100=\frac{500}{7}=\) 71.43%
Tip: A percentage of one quantity in terms of another depends only on their ratio, so a ratio given for the present answers a question about the present; the extra data on future ages is not needed here.