Question

There are five members in a family whose ages (in years ) are 40, 15, 20, 35 and 60 respectively. Two years from now, the mean of their ages will ___.

• A. remain the same
• B. increase by 2 years
• C. decrease by 2 years
• D. be reduced to half

Answer 1

The correct option is B increase by 2 years

Present ages of the five family members: 40, 15 , 20 , 35 and 60
$\text{Arithmetic mean}=\frac{\text{Sum of all observations}}{\text{Total number of observations}}$

$=\frac{40+15+20+35+60}{5}$
$=\frac{170}{5}$ $=34$

Ages of the members two years from now : 42, 17, 22, 37 and 62.
Mean of their ages two years from now is calculated as follows:
$\text{New mean}=\frac{42+17+22+37+62}{5}$
$=\frac{180}{5}=36$

Hence, two years from now, the mean age will increase by 2 years.