Question

If the mean of 25 observations is 27 and each observation is decreased by 7, what will be the new mean?

Answer 1

$Mean=\frac{\text{Sum of observations}}{\text{Total no. of observations}}$

$\Rightarrow 27=\frac{\text{Sum of observations}}{25}$

$\Rightarrow \text{Sum of observations}=27\times 25=675$

New sum =675 - (25 $\times$ 7)
= 675 - 175
=500
New mean = $\frac{500}{25}$ =20