Olibits / Math / Decimals & Measurement
Primary 5 Math: Decimals & Measurement Practice
Real Primary 5 Math questions on Decimals & Measurement, pulled directly from the Olibits question bank — the same questions a child would actually see, not separately written for this page.
MOE strand: Number and Algebra
Curriculum alignment
Mathematics Syllabus, Primary One to Six (MOE, 2021 syllabus)
Taught across P1–P6.
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Real Decimals & Measurement practice questions
Priya says: '4.5 + 3.25 = 4.75 because I just add the digits after the decimal point.' What mistake did she make?
She is completely correct
Decimals cannot be added this way at all
She did not line up the decimal places correctly - 4.50 + 3.25 = 7.75, not 4.75 ✓
She should have subtracted instead
4.5 = 4.50, so 4.50 + 3.25 = 7.75. Priya seems to have only added the decimal parts (0.50 + 0.25 = 0.75) and forgotten to add the whole-number parts.
Which working correctly converts 5 km 80 m into decimal form in km?
5.08 km, since 80 m = 0.08 km ✓
5.80 km is the same as 5.8 km which is correct
5.008 km
5.8 km, since 80 m = 0.8 km
80 m = 80/1000 km = 0.08 km, so 5 km 80 m = 5.08 km - a common mistake is writing 5.8 km by treating 80 as eight-tenths instead of eight-hundredths.
Zul says: '2.6 + 1.75 = 3.81, because I just added the digits after the decimal point: 6 + 75 = 81.' What mistake did Zul make?
He did not line up the decimal places or add the whole-number parts correctly - 2.60 + 1.75 = 4.35, not 3.81 ✓
He is completely correct
He should have subtracted instead
Decimals with different numbers of decimal places cannot be added
2.6 = 2.60, so 2.60 + 1.75 = 4.35. Zul incorrectly treated the decimal digits as separate whole numbers to add (6 + 75 = 81) instead of properly aligning and adding the full decimal numbers.