You subtracted Ali's books from Chloe's or compared the wrong students (6 − 4 = 2). The question asks about Bala and Chloe specifically.
PRIMARY 3 · MATHEMATICS
Data Analysis
Top 5 mistakes
Ranked by how often they appear across 11 MOE-aligned practice questions in our archive.
You subtracted the wrong pair of students — 9 − 6 = 3 is the difference between Bala and Ali, not Bala and Chloe. Always re-read the question to check which two values to compare.
You added Bala's and Chloe's books together (9 + 4 = 13). The question asks how many MORE, which means you need to subtract, not add.
This is the original average (80 ÷ 4 = 20), not twice it. The new target is 2 × 20 = 40.
This is B = 80 − 18 − 22 − 15 = 25, the missing bar value. The question asks for the new target.
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