Question

The average monthly wage of a group of 10 persons is Rs 9000. One member of the group, whose monthly wage is Rs 8100, leaves the group and is replaced by a new member whose monthly wages is Rs 7200. Find the new monthly average wage.

Answer 1

Average monthly wages of 10 persons = Rs 9000
Sum of the monthly wages of 10 persons = $\left(9000\times 10\right)=\mathrm{Rs}90000$
Sum of the monthly wages of 9 persons if one of the members left the group = Rs (90000 $-$ 8100) = Rs 81900
Sum of the monthly wages of 10 persons if one new member joined the group = Rs (81900 + 7200) = Rs 89100

$\therefore \mathrm{New}\mathrm{monthly}\mathrm{average}\mathrm{wages}=\frac{\mathrm{New}\mathrm{sum}\mathrm{of}\mathrm{the}\mathrm{monthly}\mathrm{wages}\mathrm{of}10\mathrm{persons}}{10}$
$$\begin{gathered} =\frac{89100}{10} \\ =\mathrm{Rs}8910 \end{gathered}$$