NDA 2017 Maths · Mathematics · Statistics · easy

The mean of five observations is 12. If one observation 8 is replaced by 18, the new mean is

Single correct option

The mean of five observations is

12

. If one observation

8

is replaced by

18

, the new mean is

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Answer: (A) $14$

The original sum is

5\times12=60

. After the replacement the sum is

60-8+18=70

, so the new mean is

\frac{70}{5}=14

. The value

12

ignores the change, and

15

adds the difference

10

without dividing by

5

and then confuses it.

Original question written in the NDA 2017 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake