Question

The mean of $5$ number is $30$. If one number is excluded their mean becomes $28$. What is the excluded number.

Answer 1

Mean of 5 number is 30.

1 number is excluded their mean become 28.

$\frac{\text{Mean of excluded number}}{5}=28$

Mean of excluded number $=140$

The mean of 5 numbers $=30$

$\frac{\text{Sum of 5 no's}}{5}=30$

Sum of 5 no's $=150$

Sum of 4 no's $+x=150$

$140+x=150$

$x=150-140$

$x=10$

$\therefore$ so excluded number is $10$.