Question

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

• A. 25
• B. 30
• C. 35
• D. 40

Answer 1

The correct option is C 35

Given,

Let $x=$ Sum of ages of teachers

$Mean=\frac{sum}{25}$

$\Rightarrow 40=\frac{sum}{25}$

$\Rightarrow x=40\times 25$

$\Rightarrow x=1000$

A new teacher appointed in place of a teacher whose age is $60$.

So, the $sum=x-60=1000-60=940$.

now a new teacher joins, and the mean falls to$39$

The new sum$=39\times 25=975$

Now, $975-940=$ Age of new teacher

Therefore, age of new teacher is $35$ years.