Added the dollars and cents in two separate columns but forgot to carry $1 when the cents exceeded 100. Computed dollars 5 + 3 = 8 and cents 45 + 80 = 125, then wrote 0.25 without adding the extra $1 to the dollar total. Result: $8.25.
PRIMARY 3 · MATHEMATICS
Money
Top 5 mistakes
Ranked by how often they appear across 37 MOE-aligned practice questions in our archive.
Mis-added the cents: thought 45 + 80 = 115 instead of 125. So cents became $1.15 carried as $1 plus 15 cents. Dollars 5 + 3 + 1 (carry) = 9. Result: $9.15.
Got cents 45 + 80 = 125 correctly but only carried 10 cents to the dollar column instead of 100 cents (i.e. carried the digit 1 as 10¢). Cents kept as 25, dollars 5 + 3 + 1 = 9, then added the leftover 10¢: $9 + 0.35 = $9.35.
Stopped after computing the total cost ($1.45 + $3.80 = $5.25) and chose that as the answer. Forgot the final step of subtracting the cost from the $20 Mei Ling started with. The cost is not the change.
Mis-added the cents in the cost: thought 45¢ + 80¢ = 135¢ instead of 125¢. Cost became $5.35; $20.00 − $5.35 = $14.65. Calc slip in the cents column.
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