In 20 litres mixture of acid, the ratio of acid and water is 2 : 3. How much water should be added to the mixture so that the ratio of the acid to water becomes 2 : 5 ?
Answer & explanation
Correct answer: option 4
Total mixture $=20$ litres.
Ratio of acid : water $=2:3$.
Quantity of acid $=\frac{2}{5}\times20=8$ litres.
Quantity of water $=\frac{3}{5}\times20=12$ litres.
Let $x$ litres of water be added.
New water $=12+x$ litres, acid remains $8$ litres.
New ratio:
$\frac{8}{12+x}=\frac{2}{5}$
$40=24+2x$
$2x=16$
$x=8$
final answer: $8$ litres of water should be added