CA Foundation · Quantitative Aptitude · Measures of Central Tendency and Dispersion
For two positive observations, the arithmetic mean is 25 and the geometric mean is 15. What is their harmonic mean?
The harmonic mean is 9. For any two positive observations the square of the geometric mean equals the product of the arithmetic and harmonic means. Therefore HM = 225 ÷ 25 = 9, which agrees with the numbers 45 and 5.
- A10
- B20
- C8
- D9Correct
Explanation
For two positive numbers, GM² = AM × HM. So HM = 15² / 25 = 225/25 = 9. Check: the numbers are 45 and 5 (sum 50, product 225), and HM = 2 × 225 / 50 = 9. The option 10 comes from wrongly subtracting GM from AM.
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