Question

A milkman mixes $4$ litres of milk with $2$ litres of water. How many litres of water is required so that he can mix it with $20$ litres of milk without getting caught?

• A. $9$ litres
• B. $8$ litres
• C. $10$ litres
• D. $12$ litres

Answer 1

The correct option is C $10$ litres

Given,
$4$ litres of milk is mixed with $2$ litres of water.

We know that
$\text{Litres of milk}\left(x\right)\propto \text{Litres of water}\left(y\right)$
$\therefore \frac{x_1}{y_1}=\frac{x_2}{y_2}$

Given,
$x_1=4$ litres
$y_1=2$ litres
$x_2=20$ litres
$\text{and}{y}_2=$ Number of litres of water needed
$y_2=\frac{x_2\times y_1}{x_1}$
$\Rightarrow y_2=\frac{20\times 2}{4}$
$\Rightarrow y_2=10$ litres
Alternate:
$4$ litres of milk is mixed with $2$ litres of water.
$1$ litres of milk is mixed with $\frac{2}{4}$ litres of water.
$20$ liters of milk is mixed with $\frac{2}{4}\times 20$ liters of water.
$\therefore$ Amount of water that can be mixed with $20$ liters of milk is $10$ liters.