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For two observations, the sum is S and product is P. What is the harmonic mean of these two observations?

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CDS Maths Previous Paper 9 (Held On: 2 Feb 2020)
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  1. \(\frac{2S}{P}\)
  2. \(\frac{S}{(2P)}\)
  3. \(\frac{2P}{S}\)
  4. \(\frac{P}{(2S)}\)

Answer (Detailed Solution Below)

Option 3 : \(\frac{2P}{S}\)
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Detailed Solution

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Given: 

The sum is S and product is P.

Formula Used:

Harmonic mean of a and b = 2/(1/a + 1/b) = 2ab/(a + b)

Calculation:

The sum is S and product is P.

Then, the Harmonic mean of these two observations = 2P/S

∴ H.M. of two observations is 2P/S

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