Primary 1 Mathematics Length Quiz

Primary 1 Mathematics Quiz - Length — Answer Key

Topic: Length Total Marks: 25 Note: Past-paper evidence for P1 Mathematics is not available. This answer key follows the Stage 4 LLM-inferred templates and the 2021 MOE Singapore Primary Mathematics Syllabus (P1–P6).

Section A: Multiple Choice (1 mark each)

1. (2) 12 cm The pencil starts at 0 cm and ends at 12 cm, so its length is read directly from the ruler: 12 cm.

• Common mistake: adding 0 + 12 to get 22 cm. Teach students to read the end mark, not to add.

2. (2) B Line B is 9 cm, which is longer than A (5 cm), C (7 cm) and D (4 cm). The longest line is B.

3. (1) cm At Primary 1, only centimetres (cm) are introduced for length. (Metres are introduced later.) The correct unit is cm.

4. (3) 8 cm The line begins at 0 and ends at the 8-cm mark. The length is read as 8 cm.

5. (1) 5 cm Compare by subtraction: 14 cm − 9 cm = 5 cm. The red ribbon is 5 cm longer.

Section B: Short Answer (1 mark each)

6. The crayon is longer (11 cm > 6 cm). When we compare two lengths, we look at which number is greater. 11 cm is greater than 6 cm, so the crayon is longer.

• Common mistake: choosing the shorter object because it "looks bigger". Always compare the actual cm values.

7. 10 cm The ribbon starts at 0 cm and ends at 10 cm. The length is read directly from the ruler: 10 cm.

8. 6 cm, 9 cm, 14 cm From smallest to largest: 6 < 9 < 14. The shortest is 6 cm and the longest is 14 cm.

9. 9 cm 17 cm − 8 cm = 9 cm. After cutting, the string is 9 cm long.

Section C: Drawing and Measuring (2 marks each)

10. 15 cm (1 mark for the number, 1 mark for the unit "cm") The toothbrush starts at 0 cm and ends at 15 cm. The length is 15 cm.

• The unit "cm" is required for full credit.

11. A line of 7 cm, drawn with a ruler starting at "•". Marking:

• 1 mark: line begins at the dot.
• 1 mark: line ends exactly at 7 cm (aligned with the 7 cm mark on a ruler).

12. AB = 4 cm, BC = 4 cm, CD = 4 cm, DA = 4 cm (1 mark for correctly measuring all four sides; 1 mark for stating the same length on every side, demonstrating that a square has equal sides). A square has four equal sides, and the grid confirms each side is 4 cm.

13. 32 cm Working: 20 cm + 12 cm = 32 cm. (1 mark for the number sentence; 1 mark for the correct answer with the unit "cm".)

14. R (13 cm), P (10 cm), Q (6 cm) From longest to shortest: 13 > 10 > 6. So the order is R, P, Q.

Section D: Word Problems (2 marks each)

15. 13 cm

• Number sentence: 18 cm − 5 cm = 13 cm
• The rope was 18 cm long. After cutting off 5 cm, the remaining rope is 13 cm.
• Marking: 1 mark for the correct number sentence; 1 mark for the correct answer with the unit "cm".

16. 4 cm

• Number sentence: 13 cm − 9 cm = 4 cm
• To find how much longer, subtract the shorter length from the longer length: 13 − 9 = 4.
• Marking: 1 mark for the correct number sentence; 1 mark for the correct answer with the unit "cm".
• Common mistake: adding the two lengths. The question asks for the difference, so we subtract.

17. 18 cm

• Number sentence: 11 cm + 7 cm = 18 cm
• Joining two lengths means adding them together: 11 + 7 = 18.
• Marking: 1 mark for the correct number sentence; 1 mark for the correct answer with the unit "cm".

18. 12 cm

• Number sentence: 20 cm − 8 cm = 12 cm
• The lace is 20 cm in total. One piece is 8 cm, so the other piece is 20 − 8 = 12 cm.
• The image shows the lace as one bar split into the 8 cm piece and the unknown piece, reinforcing the subtraction model.
• Marking: 1 mark for the correct number sentence; 1 mark for the correct answer with the unit "cm".

19. 9 cm

• Number sentence: 14 cm − 5 cm = 9 cm
• The pencil is 5 cm shorter than the eraser. Eraser = 14 cm, so pencil = 14 − 5 = 9 cm.
• Marking: 1 mark for the correct number sentence; 1 mark for the correct answer with the unit "cm".
• Common mistake: adding 14 + 5. The word "shorter" means the pencil is less, so we subtract.

20.

• (a) 7 cm. Number sentence: 16 cm − 9 cm = 7 cm. (1 mark for the number sentence; 1 mark for the answer with the unit "cm".)
• (b) 21 cm. Number sentence: 9 cm + 12 cm = 21 cm. (1 mark for the number sentence; 1 mark for the answer with the unit "cm".)

Marking Summary

Visual notes for placeholders:

• Q2: Four lines of different lengths, same starting point; B is the longest.
• Q4: Line from 0 to 8 cm on a centimetre ruler.
• Q6: Crayon (11 cm) and marker (6 cm) on a cm scale.
• Q7: Ribbon from 0 to 10 cm.
• Q10: Toothbrush from 0 to 15 cm.
• Q12: Square on a 1-cm grid, each side = 4 cm.
• Q14: Three sticks P (10 cm), Q (6 cm), R (13 cm) on a shared baseline.
• Q18: A 20-cm lace with the first 8 cm shaded as the first piece.

All lengths used are within the P1 scope (whole centimetres) and reinforce the cm-only measurement focus from the syllabus.

End of Answer Key