Question

A mixture of $40$ liters of milk and water contains $10$ $\%$ water. How much water must be added to make $20$ $\%$ water in the new mixture?

• A. $3$ liters
• B. $4$ litres
• C. $5$ litres
• D. $6$ litres

Answer 1

The correct option is C $5$ litres

$10$% of water is present in $40$ liters of milk

Hence milk $\to$ $36l$ and water $\to$ $4l$

$\frac{4+x}{40+x}=\frac{1}{5}$ ($20$% $=\frac{1}{5}$)

$20+5x=40+x$

$4x=20$

$x=5$

$5$ litres of water must be added