Question

A mixture of 40 litres of milk and water contains
10%water. How much water should be added to
it so that water may be 20% in new mixture?
1. 2.5 ltr 2. 3.5 ltr 3. 4 Itr 4. 5 ltr​

Answer 1

Total volume of mixture = 40L

water = 10% of 40 L = 4 L

Let the water added be x L.

So that the total water content now becomes (4+x) L

After adding water ---

Total Volume of mixture = (40+x) L

but water is now, 20% of total

=> water = 20% of (40+x)

=> water = (8+0.2x) L

but from earlier we know water is (4+x) L

therefore, (8+0.2x) = (4+x)

=> 8-4 = x-0.2x

=> x = 5 L

Hence the answer is 5 L water must be added.