The mean age of 25 teachers in a school is 40 years.

Question:

The mean age of 25 teachers in a school is 40 years. A teacher retires at the age of 60 years and a new teacher is appointed in his place. If the mean age of the teachers in this school now is 39 years, then the age (in years) of the newly appointed teacher is..

 

Solution:

$\frac{\sum x_{i}}{25}=40 \& \frac{\sum x_{i}-60+N}{25}=39$

Let age of newly appointed teacher is $\mathrm{N}$

$\Rightarrow 1000-60+\mathrm{N}=975$

$\Rightarrow \mathrm{N}=35$ years

 

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