Madhya Pradesh Police Exam Model Paper 7

Given:
A liquid whose price is Rs. 10 per kg has to be added to 50 kg of the solution which cost 50 per kg so that the resultant mixture cost 20 per kg.
Formula:
Ratio of two quantities = (Dearer price - mean)/(mean – cheaper price)
Calculation:
Let the amount to be added be x kg.
$\Rightarrow \left(50-20\right)/\left(20-10\right)=\mathit{x}/50$
$\Rightarrow 30/10=\mathit{x}/50$
$\Rightarrow \mathit{x}=150\mathit{k}\mathit{g}$
∴ The required quantity is 150 kg.