Primary 2 Mathematics Length Mass Volume Quiz

Primary 2 Mathematics Quiz - Length Mass Volume: Answer Key

Total Marks: 20

Section A: Length (Questions 1 to 5)

1. C. metres (m)

• Marks: 1
• Explanation: Metres (m) are used to measure longer lengths, like the length of a classroom. Grams measure mass, litres measure volume, and kilograms measure mass. So, metres is the correct unit for length.
• Common mistake: Students might choose grams or kilograms because they are common units, but they measure mass, not length.

2. B. A ruler that is 30 cm long

• Marks: 1
• Explanation: 30 cm is longer than 15 cm. The ruler is twice as long as the pencil.
• Common mistake: Students might not compare the numbers correctly. Remind them that a bigger number means a longer length when using the same unit (cm).

3. 200 cm

• Marks: 1
• Explanation: 1 m = 100 cm. So, 2 m = 2 × 100 cm = 200 cm.
• Working: 2 × 100 = 200
• Common mistake: Students might think 1 m = 10 cm or 1 m = 1000 cm. Emphasise that 1 metre is equal to 100 centimetres.

4. The paintbrush

• Marks: 1
• Explanation: The paintbrush is 14 cm long, the crayon is 8 cm long, and the glue stick is 6 cm long. 14 cm is the longest.
• Common mistake: Students might misread the labels or not compare all three lengths.

5. 80 cm

• Marks: 1
• Explanation: Total length = 50 cm + 30 cm = 80 cm.
• Working: 50 + 30 = 80
• Common mistake: Students might subtract instead of adding. The word "total" means we need to add the lengths together.

Section B: Mass (Questions 6 to 10)

6. C. kilograms (kg)

• Marks: 1
• Explanation: Kilograms (kg) are used to measure the mass of heavier objects like a bag of rice. Metres measure length, litres measure volume, and centimetres measure length.
• Common mistake: Students might choose litres because rice is a substance, but litres measure volume of liquids, not mass.

7. 2 kg

• Marks: 1
• Explanation: Difference = 3 kg - 1 kg = 2 kg. The watermelon is 2 kg heavier.
• Working: 3 - 1 = 2
• Common mistake: Students might add instead of subtract. "How much heavier" means we find the difference by subtracting.

8. 4 kg

• Marks: 1
• Explanation: Each bag of sugar is 2 kg. Total mass = 2 kg + 2 kg = 4 kg.
• Working: 2 + 2 = 4
• Common mistake: Students might only count one bag of sugar or misread the labels.

9. 600 g

• Marks: 1
• Explanation: Total mass = 400 g + 200 g = 600 g.
• Working: 400 + 200 = 600
• Common mistake: Students might forget to include the unit (g) in their answer.

10. C. They are the same

• Marks: 1
• Explanation: Both bags have a mass of 1 kg. Even though feathers are lighter than stones, the bags have the same mass because they both weigh 1 kg.
• Common mistake: Students might think stones are heavier because they are denser. Emphasise that mass is the amount of matter, and 1 kg of anything has the same mass as 1 kg of anything else.

Section C: Volume (Questions 11 to 15)

11. B. litres (ℓ)

• Marks: 1
• Explanation: Litres (ℓ) are used to measure the volume of liquids like water. Grams measure mass, metres measure length, and kilograms measure mass.
• Common mistake: Students might choose grams or kilograms because they are common, but they measure mass, not volume.

12. 15 ℓ

• Marks: 1
• Explanation: Total volume = 10 ℓ + 5 ℓ = 15 ℓ.
• Working: 10 + 5 = 15
• Common mistake: Students might subtract instead of adding. "Added" means we need to add the volumes.

13. Jug B

• Marks: 1
• Explanation: Jug B has 4 ℓ of water, and Jug A has 2 ℓ of water. 4 ℓ is more than 2 ℓ.
• Common mistake: Students might misread the water levels or not compare the numbers correctly.

14. 1000 ml

• Marks: 1
• Explanation: 1 ℓ = 1000 ml.
• Common mistake: Students might think 1 ℓ = 100 ml or 1 ℓ = 10 ml. Emphasise that 1 litre is equal to 1000 millilitres.

15. 5 ℓ

• Marks: 1
• Explanation: Difference = 8 ℓ - 3 ℓ = 5 ℓ. The pail has 5 ℓ more water.
• Working: 8 - 3 = 5
• Common mistake: Students might add instead of subtract. "How much more" means we find the difference by subtracting.

Section D: Mixed Questions (Questions 16 to 20)

16. 50 cm, 1 m, 150 cm, 2 m

• Marks: 1
• Explanation: First, convert all measurements to the same unit (cm): 2 m = 200 cm, 1 m = 100 cm, 150 cm = 150 cm, 50 cm = 50 cm. Then arrange: 50 cm, 100 cm (1 m), 150 cm, 200 cm (2 m).
• Working: 2 m = 200 cm, 1 m = 100 cm. Order: 50 cm, 100 cm, 150 cm, 200 cm.
• Common mistake: Students might not convert all measurements to the same unit before comparing. Remind them to use the same unit for accurate comparison.

17. 3 kg 500 g

• Marks: 1
• Explanation: 2 kg + 1 kg = 3 kg. 0 g + 500 g = 500 g. Total = 3 kg 500 g.
• Working: 2 kg + 1 kg = 3 kg. 0 g + 500 g = 500 g. Total = 3 kg 500 g.
• Common mistake: Students might forget to add the grams separately or might incorrectly convert 500 g to 0.5 kg without showing the mixed unit.

18. 8 ℓ

• Marks: 1
• Explanation: Total volume = 1 ℓ + 2 ℓ + 5 ℓ = 8 ℓ.
• Working: 1 + 2 + 5 = 8
• Common mistake: Students might misread the labels or forget to add all three volumes.

19. 3 m

• Marks: 1
• Explanation: The rope is 2 m longer than the string. So, rope length = 1 m + 2 m = 3 m.
• Working: 1 + 2 = 3
• Common mistake: Students might subtract instead of add. "Longer than" means we add the difference to the original length.

20. 3 kg

• Marks: 1
• Explanation: Difference = 7 kg - 4 kg = 3 kg. The dog is 3 kg heavier.
• Working: 7 - 4 = 3
• Common mistake: Students might add instead of subtract. "Difference" means we subtract the smaller number from the larger number.