RRB NTPC 2014 Paper

(2) Suppose he sells x lemons at 25% profit and (100 – x) at 10%profit.
Let cost price of one lemon be ₹1.Selling price of x lemons =
$\mathit{x}+\mathrm{}\frac{\mathit{x}}{4}=\mathrm{}\frac{5\mathit{x}}{4}$
Selling price of (100 – x) lemons =
$\left(100-\mathit{x}\right)+\mathrm{}\frac{1}{10}\left(100-\mathit{x}\right)$
$=1.1\left(100-\mathit{x}\right)=110-1.1\mathit{x}$
Net profit =
$\frac{110-1.1\mathit{x}+\mathrm{}\frac{5\mathit{x}}{4}-100}{100}\times 100=16$
$\Rightarrow 10+0.15\mathit{x}=16$
$\Rightarrow \mathit{x}=\mathrm{}\frac{6}{0.15}=40$