Question

12 litre of mix of acid & water contain 30% acid.How much litre of water should be withdrawn to make acid 40%?​

Answer 1

Answer:

If you add 25 l of water, total volume will be 50 litres. There is 5 l of acid in it, being 20% of 25 litres. Now the acid (5 litres) will be 10% of the total (50 litres).

Steps.

Let x be the water added. Total volume is 25+x.

The acid present is 20% of 25 litres i.e. 5 litres.

5 litres of acid in 25+x litres is (5/25+x) X 100 = 10. Solving you get the value of x as 25.

Answer 2

Answer:

30% acid concentration have acid,

$\frac{30}{100} \times 12 = 3.6 \: l$

Remaining water

$12 - 3.6 = 8.4 \: l$

So,

For 40% acid concentration

3.6 = 40% of x

$x = \frac{ 3.6 \times 100}{40} = 9 \:l$

Water = 9 - 3.6 = 5.4

So for making 40 % concentration

8.4 - 5.4 = 3 liter wate should be withdrawn.