HOTS Mathematics Primary 6 Ratio

Ravi mixes red and blue paint in the ratio 3 : 5. He adds 6 litres of red paint. The new ratio of red to blue paint is 3 : 4. How many litres of blue paint does Ravi have?

A 24
B 32
C 40
D 48
Show Worked Solution

Worked Solution

Step 1: Let red = 3k and blue = 5k (original ratio 3:5). Step 2: After adding 6 L of red: red = 3k + 6. Blue stays at 5k. Step 3: New ratio: (3k + 6) / 5k = 3 / 4. Step 4: Cross-multiply: 4(3k + 6) = 3(5k) → 12k + 24 = 15k → 3k = 24 → k = 8. Step 5: Blue paint = 5k = 5 × 8 = 40 litres.

Correct answer: 40

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