SSC CPO SI and ASI Model Paper 7

(1) Let the original averageexpenditure of electricity bill for onestudent per day be ₹x.Sum of per day expenditure of 10students = ₹10x
Sum of per day expenditure of 15students = $\mathit{₹}15\left(\mathit{x}\mathit{–}2\right)$
According to the question,
$15\left(\mathit{x}\mathit{–}2\right)\mathit{–}10\mathit{x}=50$
$\Rightarrow 15\mathit{x}\mathit{–}30\mathit{–}10\mathit{x}=50$
$\Rightarrow 5\mathit{x}=80$
$\Rightarrow \mathit{x}=16$
∴ Original expenditure on electricitybill per day $=\mathit{₹}16\times 10=\mathit{₹}160$