CA Foundation · Quantitative Aptitude · Sequence and Series
If three numbers 1/2, 1/x and 1/8 are in harmonic progression, what is the value of x?
The value of x is 5. When terms are in harmonic progression, their reciprocals are in arithmetic progression. The reciprocals are 2, x and 8, so x is the average of 2 and 8, which is 5.
- A5Correct
- B4
- C5.5
- D6
Explanation
Reciprocals 2, x, 8 must be in AP, so x is their arithmetic mean: (2 + 8)/2 = 5. The value 4 is the geometric mean of 2 and 8, which would apply only if the reciprocals were in GP.
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