HOTS Mathematics Primary 6 Ratio

3/7 of Auntie Lim's kueh lapis are pandan-flavoured and the rest are original flavour. She then bakes 14 more original-flavour kueh lapis. Now 1/3 of all her kueh lapis are pandan-flavoured. How many pandan-flavoured kueh lapis does she have?

A 28
B 14
C 42
D 21
Show Worked Solution

Worked Solution

Step 1: Pandan : Original = 3 : 4 (from 3/7 pandan means 4/7 original). Let pandan = 3k, original = 4k. Step 2: After baking 14 more original: original = 4k + 14. Pandan unchanged at 3k. New total = 7k + 14. Step 3: Pandan is now 1/3 of total: 3k / (7k + 14) = 1/3. Step 4: Cross-multiply: 9k = 7k + 14 → 2k = 14 → k = 7. Step 5: Pandan = 3k = 3 × 7 = 21.

Correct answer: 21

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