Question

A solution consists acid and water in the ratio 5:3. If 4 litres of water is added, the new ratio becomes 5:4. What is the original quantity of acid in the solution?

• A. 20 litres
• B. 25 litres
• C. 30 litres
• D. 35 litres

Answer 1

Answer:

A. 20 litres

Let the original quantities be:

• Acid = (5x) litres

• Water = (3x) litres

After adding 4 litres of water:

• Acid = (5x)

• Water = (3x + 4)

Given the new ratio is (5:4):

$\frac{5x}{3x+4}=\frac{5}{4}$

Cross-multiplying:

20x = 15x + 20

5x = 20

x = 4

Therefore, the original quantity of acid was:

$5x = 5 \times 4 = 20$

✅ Original quantity of acid = 20 litres.