The present ages of two sisters are in the ratio 4 : 5. After 6 years the ratio will be 5 : 6. What is the elder sister's present age?

Correct answer: D. 30 years

Let the ages be 4k and 5k. (4k + 6) : (5k + 6) = 5 : 6 gives 24k + 36 = 25k + 30, so k = 6. The elder sister is 5 × 6 = 30 years old.

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Answer and explanation

The correct answer is D. 30 years

Let the ages be 4k and 5k. (4k + 6) : (5k + 6) = 5 : 6 gives 24k + 36 = 25k + 30, so k = 6. The elder sister is 5 × 6 = 30 years old.