Question

A mixture of water and milk is $40$ litres. There is $10$% water in it. How much water should now be added in this mixture so that the new mixture contains $20$% water?

• A. $4$ litres
• B. $5$ litres
• C. $6.5$ litres
• D. $7.5$ litres

Answer 1

Answer: (B)

$5$ litres

$\Rightarrow$ 10% of 40 liters is 4 liters.

$\Rightarrow$ To make it 20% water, you will have to add ${}^{\prime }{x}^{\prime }$ liters of water to the mixture.

$\Rightarrow$ $\frac{(x+4)}{(x+40)}=\frac{20}{100}$

$\Rightarrow$ $x+4=(x+40)\times 0.2$

$\Rightarrow$ $x+4=0.2x+8$

$\Rightarrow$ $0.8x=4$

$\therefore$ $x=5$

$\therefore$ Water should be added in mixture is $5liters$.