RRB RPF RPSF SI and CONS Model Papers 2 with solutions

(a) Given that,
Number of male employees (M) = 45
Number of female employees (F) = 15
Mean salary of male employee $\left({\overline{\mathit{x}}}_{\mathit{M}}\right)$= ₹ 5000
Total number of employees = (M + F)= 45 + 15 = 60
Mean salary of employees $\left({\overline{\mathit{x}}}_{\mathit{M}\mathit{F}}\right)$ = ₹ 4800
Let mean salary of female employee is ${\overline{\mathit{x}}}_{\mathit{F}}$
By formula,
${\overline{\mathit{x}}}_{\mathit{M}\mathit{F}}=\frac{\mathit{M}{\overline{\mathit{x}}}_{\mathit{M}}+\mathit{F}{\overline{\mathit{x}}}_{\mathit{F}}}{\left(\mathit{M}+\mathit{F}\right)}$
$\Rightarrow 4800=\mathrm{}\frac{45\times 5000+15\times {\overline{\mathit{x}}}_{\mathit{F}}}{60}$
$\Rightarrow 4800\times 60-45\times 5000=15\times {\overline{\mathit{x}}}_{\mathit{F}}$
∴ ${\overline{\mathit{x}}}_{\mathit{F}}=4800\times 4-3\times 5000$
$=300\left(16\times \mathit{e}\mathit{s}4-50\right)=300\times 14=4200$