The student counted only the 3 marks after the 10 cm line, reading 10, 11, 12, 13 as 3 instead of reading the full measurement of 13 cm.
PRIMARY 1 · MATHEMATICS
Length and Mass
Top 5 mistakes
Ranked by how often they appear across 23 MOE-aligned practice questions in our archive.
The student misread the ruler and stopped at the 8 cm mark instead of following the pencil all the way to its tip at 13 cm.
The student added 5 extra centimetres, reading 13 + 5 = 18 cm, perhaps counting past the tip of the pencil.
The student used 100 cm for 2 m instead of 200 cm, then calculated 100 - 75 = 25 cm. This shows confusion about how many centimetres are in 1 metre.
The student correctly converted 2 m to 200 cm but subtracted 10 cm too many, calculating 200 - 85 = 115 cm instead of 200 - 75 = 125 cm.
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