Question

The arithmetic mean of 12 observations is 15 If two observations 20 and 25 are removed then the arithmetic mean of remaining observations is

• A. $14.5$
• B. $13.5$
• C. $12.5$
• D. $13$

Answer 1

The correct option is B $13.5$

Arithmetic mean of 12 observations is 15.
Thus, sum of 12 observations = 180
After removing 25 and 20 from the series, sum of 10 observations = $180-25-20=135$
Thus, mean = $\frac{sum}{number}$ = $\frac{135}{10}=13.5$