Question

There is a 21 litres mixture of milk and water. The ratio of milk and water in the mixture is 4: 3. Find the amount of water (in litres) that should be added to this mixture so that the resulting mixture has 50% of water in it.

• A. 4
• B. 1
• C. 3
• D. 2

Answer 1

Answer:

C. 3

Total mixture = 21 L
Ratio (Milk : Water) = 4 : 3

Find initial quantities

Total parts = 4 + 3 = 7

• Milk = $( \frac{4}{7} \times 21 = 12 ) L$

• Water = $( \frac{3}{7} \times 21 = 9 ) L$

• Let x litres of water be added

New:

• Water = (9 + x)

• Total mixture = (21 + x)

  Condition given

Water should be 50% of mixture

$9 + x = \frac{1}{2}(21 + x)$

Solve equation

18 + 2x = 21 + x

2x - x = 21 - 18

x = 3

Final Answer: 3 litres