CA Foundation · Quantitative Aptitude · Ratio and Proportion, Indices and Logarithms
If 6, x and 24 are in continued proportion with x positive, and the third proportional to 6 and x is y, what is the value of x + y?
x is the mean proportional of 6 and 24, so x = 12. The third proportional to 6 and 12 is 12²/6 = 24. The sum is 12 + 24 = 36.
- A36
- B48Correct
- C60
- D72
Explanation
For continued proportion 6 : x = x : 24, so x² = 144 and x = 12. The third proportional y to 6 and 12 satisfies 6 : 12 = 12 : y, so y = 144/6 = 24. Hence x + y = 12 + 24 = 36. Wait, recheck: the sum is 36, so option 36 is correct.
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