Forgot to apply the $5.00 voucher (computed 50 - (3 x 7.50 + 2 x 4) = 50 - 30.50 = 19.50, then arithmetic slip to 14.50).
PRIMARY 5 · MATHEMATICS
Whole Numbers
Top 5 mistakes
Ranked by how often they appear across 38 MOE-aligned practice questions in our archive.
Added the voucher to the cost instead of subtracting it: 50 - (22.50 + 8 + 5) = 17.50.
Computed 50 - 3 x 7.50 - 5 = 22.50, missing the magazines purchase entirely.
This answer treats all operations as left-to-right addition and subtraction: 6 + 3 = 9, 9 + 4 = 13, 13 − 2 = 11. It incorrectly ignores the multiplication sign between 3 and 4. Multiplication must be performed BEFORE addition and subtraction.
This answer adds 6 + 3 first to get 9, then multiplies by 4 to get 36, then subtracts 2 to get 34. This ignores the order of operations — you must do multiplication BEFORE addition. The correct method is: 3 × 4 = 12 first, THEN 6 + 12 − 2 = 16.
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