Question

In a $729ml$ mixture milk and water are in the ratio of $7:2$.. How much quantity of water should be added in the new mixture so that the ratio of milk and water becomes $7:3$?

• A. $72ml$
• B. $85ml$
• C. $81ml$
• D. $90ml$

Answer 1

Answer: (C)

Original quantity of water in $729ml$ mixture $=\frac{2}{9}\times 729=162ml$
Let the $x$ ltr. of water is added to form the milk and water ratio as $7:3$
Equating amount of water after addiction
So $\frac{3}{10}(729+x)=162+x$
$\Rightarrow 2187+3x=1620+10x$
$\Rightarrow 567=7x\Rightarrow x=81ml$
Hence, option $B$ is the correct answer.