- Home
- Standard 13
- Quantitative Aptitude
4.Average
medium
Out of $30$ teachers of a school, a teacher of age $60$ $years$ retired. In his place another teacher of age $30$ $years$ was appointed. As a result, the mean age of the teachers will
A
remain same
B
decrease by $2$ years
C
decrease by $6$ months
D
decrease by $1$ year
Solution
Initial number of teachers $=30$
Let initial average age be $x$ years.
Average $=\frac{\text { Sum of ages }}{\text { number of persons }}$
Total initial age $=30 x$
Total final age of teachers $=30 x-60+30=30 x-30$
Number of teachers $=30$
New average $=\frac{30 x-30}{30}=x-1$
$\therefore$ Average decrease by $1$
Standard 13
Quantitative Aptitude
