Question

A container has 30 L of water. If 3 L of water is replaced by 3 L of spirit and this operation is repeated twice, what will be the quantity of water in the new mixture?

• A. 24 L
• B. 23 L
• C. 24.3 L
• D. 23.3 L
• E. None of these

Answer 1

The correct option is C 24.3 L

Here,
We apply the formula,
Quantity of pure liquid left
$=y{(1-\frac{x}{y})}^{n}units$
Here, y =Quantity of pure liquid
x =Quantity replaced
So, quantity of water =30
${(1-\frac{3}{30})}^2=30{(1-\frac{1}{10})}^2=30\times {\left(\frac{9}{10}\right)}^2=30\times 0.81=24.3L$