###
**20 litres of a mixture contains milk and water in the ratio 3 : 1. Then the amount of milk to be added to the mixture so as to have milk and water in ratio 4 : 1 is-**

A. 7 litres
B. 4 litres
C. 5 litres
D. 6 litres
**Answer: Option C**

## Show Answer

Solution(By Apex Team)

$\begin{aligned}&\text{In 20 litres of mixture}\\
&\text{Quantity of milk}\\
&\Rightarrow\frac{3}{4}\times20=15\text{ litres }\\
&\text{Quantity of water}\\
&\Rightarrow\frac{1}{4}\times20=5\text{ litres }\end{aligned}$
Let the quantity of milk added be x litres.
According to the question,
$\begin{aligned}&\Rightarrow\frac{15+x}{5}=\frac{4}{1}\\
&\Rightarrow15+x=4\times5\\
&\Rightarrow x=20-15\\
&\Rightarrow x=5\text{ litres }\end{aligned}$

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