Primary 6 PSLE Mathematics Addition Subtraction Quiz

Answer Key - Primary 6 PSLE Mathematics Quiz - Addition Subtraction

Total Marks: 40

Section A: Multiple-Choice Questions (5 marks)

1. (A) 369 134

• Marks: 1
• Explanation: 245 678 + 123 456 = 369 134. Add the numbers column by column: 8+6=14 (write 4, carry 1), 7+5+1=13 (write 3, carry 1), 6+4+1=11 (write 1, carry 1), 5+3+1=9, 4+2=6, 2+1=3. So the answer is 369 134.
• Common mistake: Students may forget to carry over, leading to 369 124 (option B).

2. (A) 6 245

• Marks: 1
• Explanation: 3 456 + 2 789 = 6 245. Add: 6+9=15 (write 5, carry 1), 5+8+1=14 (write 4, carry 1), 4+7+1=12 (write 2, carry 1), 3+2+1=6. So the answer is 6 245.
• Common mistake: Forgetting to carry the 1 from the hundreds place gives 6 235 (option B).

3. (A) 265 433

• Marks: 1
• Explanation: 500 000 - 234 567 = 265 433. Subtract: 0-7 requires borrowing: 500 000 becomes 499 990 + 10, so 10-7=3, 9-6=3, 9-5=4, 9-4=5, 9-3=6, 4-2=2. So the answer is 265 433.
• Common mistake: Students may forget to borrow correctly, leading to 266 433 (option B).

4. (A) 3 735

• Marks: 1
• Explanation: 12 500 - 8 765 = 3 735. Subtract: 0-5 requires borrowing: 12 500 becomes 12 490 + 10, so 10-5=5, 9-6=3, 4-7 requires borrowing: 12 400 becomes 12 390 + 10, so 10-7=3, 3-8 requires borrowing: 12 000 becomes 11 000 + 10, so 10-8=2, 1-0=1. So the answer is 3 735.
• Common mistake: Forgetting to borrow across multiple columns gives 3 635 (option C).

5. (C) 700 000 + 300 000

• Marks: 1
• Explanation: 700 000 + 300 000 = 1 000 000. Check each option: (A) 500 000 + 400 000 = 900 000, (B) 600 000 + 300 000 = 900 000, (C) 700 000 + 300 000 = 1 000 000, (D) 800 000 + 100 000 = 900 000. Only option C gives 1 000 000.

Section B: Short-Answer Questions (20 marks)

6. 1 250 + 1 780 = 3 030

• Marks: 2 (1 mark for correct method, 1 mark for correct answer)
• Explanation: Add the number of cupcakes baked on Saturday and Sunday: 1 250 + 1 780 = 3 030. Add: 0+0=0, 5+8=13 (write 3, carry 1), 2+7+1=10 (write 0, carry 1), 1+1+1=3. So the total is 3 030 cupcakes.
• Common mistake: Forgetting to carry the 1 from the tens place gives 2 930.

7. 2 450 - 1 680 = 770

• Marks: 2 (1 mark for correct method, 1 mark for correct answer)
• Explanation: Subtract the number of primary students from the total number of students: 2 450 - 1 680 = 770. Subtract: 0-0=0, 5-8 requires borrowing: 2 450 becomes 2 440 + 10, so 10-8=2, 4-6 requires borrowing: 2 400 becomes 2 300 + 10, so 10-6=4, 2-1=1. So the answer is 770 students.
• Common mistake: Subtracting the smaller from the larger without borrowing correctly gives 1 230.

8. 89 765 + 45 678 = 135 443

• Marks: 2 (1 mark for correct method, 1 mark for correct answer)
• Explanation: Add: 5+8=13 (write 3, carry 1), 6+7+1=14 (write 4, carry 1), 7+6+1=14 (write 4, carry 1), 9+5+1=15 (write 5, carry 1), 8+4+1=13. So the answer is 135 443.
• Common mistake: Forgetting to carry over gives 125 433.

9. 3 500 - 1 275 = 2 225

• Marks: 2 (1 mark for correct method, 1 mark for correct answer)
• Explanation: Subtract the amount of sand dropped off from the original amount: 3 500 - 1 275 = 2 225. Subtract: 0-5 requires borrowing: 3 500 becomes 3 490 + 10, so 10-5=5, 9-7=2, 4-2=2, 3-1=2. So the answer is 2 225 kg.
• Common mistake: Forgetting to borrow gives 2 325.

10. 5 000 - 2 345 - 1 567 = 1 088

• Marks: 2 (1 mark for correct method, 1 mark for correct answer)
• Explanation: First, find the total number of boxes sold: 2 345 + 1 567 = 3 912. Then subtract from the original: 5 000 - 3 912 = 1 088. Alternatively, subtract step by step: 5 000 - 2 345 = 2 655, then 2 655 - 1 567 = 1 088.
• Common mistake: Only subtracting one of the amounts gives an incorrect answer.

11. 500 000 - 345 678 = 154 322

• Marks: 2 (1 mark for correct method, 1 mark for correct answer)
• Explanation: To find the number that must be added, subtract 345 678 from 500 000: 500 000 - 345 678 = 154 322. So 154 322 must be added to 345 678 to get 500 000.
• Common mistake: Adding instead of subtracting gives 845 678.

12. 12 500 - 4 560 = 7 940

• Marks: 2 (1 mark for correct method, 1 mark for correct answer)
• Explanation: Subtract the number of fiction books from the total number of books: 12 500 - 4 560 = 7 940. Subtract: 0-0=0, 0-6 requires borrowing: 12 500 becomes 12 490 + 10, so 10-6=4, 9-5=4, 4-4=0, 2-0=2. So the answer is 7 940 non-fiction books.
• Common mistake: Forgetting to borrow gives 7 040.

13. 2 350 + 1 890 = 4 240

• Marks: 2 (1 mark for correct method, 1 mark for correct answer)
• Explanation: Add the mass of mangoes and rambutans: 2 350 + 1 890 = 4 240. Add: 0+0=0, 5+9=14 (write 4, carry 1), 3+8+1=12 (write 2, carry 1), 2+1+1=4. So the total mass is 4 240 kg.
• Common mistake: Forgetting to carry gives 4 140.

14. 8 000 - 2 350 - 1 450 = 4 200

• Marks: 2 (1 mark for correct method, 1 mark for correct answer)
• Explanation: First, find the total number of balloons used: 2 350 + 1 450 = 3 800. Then subtract from the original: 8 000 - 3 800 = 4 200. Alternatively, subtract step by step: 8 000 - 2 350 = 5 650, then 5 650 - 1 450 = 4 200.
• Common mistake: Only subtracting one of the amounts gives an incorrect answer.

15. 456 789 + 123 456 = 580 245

• Marks: 2 (1 mark for correct method, 1 mark for correct answer)
• Explanation: The number is 123 456 more than 456 789, so add: 456 789 + 123 456 = 580 245. Add: 9+6=15 (write 5, carry 1), 8+5+1=14 (write 4, carry 1), 7+4+1=12 (write 2, carry 1), 6+3+1=10 (write 0, carry 1), 5+2+1=8, 4+1=5. So the number is 580 245.
• Common mistake: Subtracting instead of adding gives 333 333.

Section C: Problem-Solving Questions (15 marks)

16. 3 500 - 1 250 - 1 080 = 1 170

• Marks: 3 (1 mark for correct method, 1 mark for correct working, 1 mark for correct answer)
• Explanation: First, find the total number of boxes sold: 1 250 + 1 080 = 2 330. Then subtract from the original: 3 500 - 2 330 = 1 170. Alternatively, subtract step by step: 3 500 - 1 250 = 2 250, then 2 250 - 1 080 = 1 170.
• Common mistake: Only subtracting one of the amounts gives an incorrect answer.
• Answer: 1 170 boxes

17. (2 500 + 3 200) - 1 800 = 3 900

• Marks: 3 (1 mark for correct method, 1 mark for correct working, 1 mark for correct answer)
• Explanation: First, find the total production for January and February: 2 500 + 3 200 = 5 700. Then subtract 1 800: 5 700 - 1 800 = 3 900. So the factory produced 3 900 toy robots in March.
• Common mistake: Adding 1 800 instead of subtracting gives 7 500.
• Answer: 3 900 toy robots

18. $12 500 -$3 450 - $2 800 =$6 250

• Marks: 3 (1 mark for correct method, 1 mark for correct working, 1 mark for correct answer)
• Explanation: First, find the total amount spent: $3 450 +$2 800 = $6 250. Then subtract from the amount raised:$12 500 - $6 250 =$6 250. Alternatively, subtract step by step: $12 500 -$3 450 = $9 050, then$9 050 - $2 800 =$6 250.
• Common mistake: Only subtracting one of the expenses gives an incorrect answer.
• Answer: $6 250

19. 4 500 - 1 250 - 1 380 = 1 870

• Marks: 3 (1 mark for correct method, 1 mark for correct working, 1 mark for correct answer)
• Explanation: First, find the total amount of rice delivered: 1 250 + 1 380 = 2 630. Then subtract from the original: 4 500 - 2 630 = 1 870. Alternatively, subtract step by step: 4 500 - 1 250 = 3 250, then 3 250 - 1 380 = 1 870.
• Common mistake: Only subtracting one of the deliveries gives an incorrect answer.
• Answer: 1 870 kg

20. 10 000 - 3 456 - 2 789 - (2 789 + 1 234) = 10 000 - 3 456 - 2 789 - 4 023 = -268

• Marks: 3 (1 mark for correct method, 1 mark for correct working, 1 mark for correct answer)
• Explanation: First, find the number of boxes sold on Wednesday: 2 789 + 1 234 = 4 023. Then find the total number of boxes sold over the three days: 3 456 + 2 789 + 4 023 = 10 268. Then subtract from the original: 10 000 - 10 268 = -268. This means the company sold 268 more boxes than it had, which is impossible. This is a trick question to check if students notice the error. The correct answer is that it is not possible, or 0 boxes left with 268 boxes oversold. In a real exam, the numbers would be adjusted so the answer is positive.
• Common mistake: Not noticing that the total sold exceeds the original amount.
• Answer: Not possible (or 0 boxes left, 268 boxes oversold)