If water is mixed with milk to gain 20% by selling the mixture at cost price. Then ratio of water to milk in mixture, is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 1 : 5 **
Let cost price of milk per litre = 1 (water is free).
Let milk = 1 litre, water = x litres.
Total cost = 1
Total volume = 1 + x
Cost price of mixture per litre = $\frac{1}{1+x}$
Selling price per litre = cost price of milk = $1$
Given gain = $20\% = 0.2$
$\frac{1 - \frac{1}{1+x}}{\frac{1}{1+x}} = 0.2$
$x = 0.2$
Ratio of water : milk = $0.2 : 1 = \frac{1}{5}$
The required ratio is $1 : 5$.