. The mean of certain number of observations is 46. If four observation whose mean is 52 are removed, the mean becomes 44.5. The original number of obse


A. 35
B. 20
C. 15
D. 12

 

Best Answer

Answer ||| B Solution ||| Let the number of observations be ‘n’. So, sum of ‘n’ observations = 46 × n Sum of 4 numbers being removed = 52 × 4 = 208 So, now sum of (n – 4) observations = 44.5 × (n – 4) ⇒ Sum of (n – 4) observations = Sum of n observations – Sum of 4 numbers ⇒ 44.5 × (n – 4) = 46 × n – 208 ⇒ 44.5 × n – 178 = 46 × n – 208 ⇒ 1.5n = 208 – 178 = 30 ⇒ n = 20 So, the answer is 20 observations (option B).

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