Primary 4 Mathematics Semestral Assessment 1 (Mid-Year) Paper 1

Answer Key & Marking Scheme

Primary 4 Mathematics – SA1 (Whole Numbers)

Version: 1 of 5

General Marking Notes:

• Method marks (M) are awarded for correct working steps even if the final answer is wrong.
• Answer marks (A) are awarded for the correct final answer.
• Units (e.g., books, $) are required for word problems unless the question asks for a number only.
• Spelling errors in numbers written in words may result in loss of marks if the meaning is ambiguous.

Section A: Multiple Choice Questions (10 Marks)

1. (4)

• Reasoning: The digit 8 is in the thousands place. Its value is $8 \times 1,000 = 8,000$.
• Common Mistake: Choosing (3) 800 (hundreds place) or (2) 80 (tens place).

2. (4)

• Reasoning: Compare the ten-thousands digit (all are 6). Compare the thousands digit: 0, 1, 0, 1. The numbers with 1 in the thousands place are 61,001 and 61,010. Compare the tens/ones: 61,010 > 61,001.
• Common Mistake: Choosing (2) 61,001 without checking the last two digits.

3. (2)

• Reasoning: "Seventy-two thousand" = 72,000. "and forty-five" = 45. Combined: 72,045. Note the zero in the hundreds place.
• Common Mistake: Choosing (1) 72,450 (misinterpreting "forty-five" as 450) or (4) 72,405.

4. (4)

• Reasoning: To round 54,872 to the nearest thousand, look at the hundreds digit (8). Since $8 \ge 5$, round up the thousands digit. $54,000 \rightarrow 55,000$.
• Common Mistake: Rounding down to 54,000.

5. (2)

• Reasoning: Smallest to Largest.
  • 30,050 (Smallest)
  • 30,500
  • 35,000 (Largest)
• Common Mistake: Confusing ascending and descending order.

6. (2)

• Reasoning: $24,500 + 15,500$.
  • $500 + 500 = 1,000$ (carry over 1)
  • $4 + 5 + 1 = 10$ (carry over 1)
  • $2 + 1 + 1 = 4$
  • Result: 40,000.

7. (2)

• Reasoning: $9,850 + 10,150$.
  • $850 + 150 = 1,000$
  • $9,000 + 10,000 + 1,000 = 20,000$.

8. (1)

• Reasoning: "10,000 less" means subtraction. $82,450 - 10,000 = 72,450$. Only the ten-thousands digit changes.

9. (2)

• Reasoning: The pattern increases by 100 each time ($12,600 - 12,500 = 100$).
  • $12,700 + 100 = 12,800$.
  • Check: $12,800 + 100 = 12,900$. Correct.

10. (2)

• Reasoning: Compare 45,678 and 45,687.
  • Ten-thousands, thousands, and hundreds are the same (45,6xx).
  • Tens digit: 7 vs 8. Since $8 > 7$, 45,687 is larger. Town B is larger.

Section B: Short Answer Questions (10 Marks)

11. 3

• Reasoning: In 93,047:
  • 7 is in the ones place.
  • 4 is in the tens place.
  • 0 is in the hundreds place.
  • 3 is in the thousands place.
  • 9 is in the ten-thousands place.

12. 67,400

• Reasoning: Round 67,439 to the nearest hundred.
  • Look at the tens digit: 3.
  • Since $3 < 5$, round down (keep the hundreds digit same).
  • Result: 67,400.

13. 37,777

• Working: $$\begin{array}{r} 23,456 \\ + 14,321 \\ \hline 37,777 \end{array}$$
• Note: No carrying is required in this specific sum.

14. 41,500

• Working: $$\begin{array}{r} 50,000 \\ - \phantom{0}8,500 \\ \hline 41,500 \end{array}$$
• Method: $50,000 - 8,000 = 42,000$. $42,000 - 500 = 41,500$.

15. 44,400, 44,000, 40,400, 40,040

• Reasoning: Descending means largest to smallest.
  1. 44,400 (Largest)
  2. 44,000
  3. 40,400
  4. 40,040 (Smallest)

Section C: Structured Questions (30 Marks)

16. Bookstore Sales (a) Books sold in the second week [2 marks]

• Concept: "3,200 more than" means addition.
• Working: $12,450 + 3,200 = 15,650$
• Answer: 15,650 books

(b) Total books sold in two weeks [2 marks]

• Concept: Sum of Week 1 and Week 2.
• Working: $12,450 \text{ (Week 1)} + 15,650 \text{ (Week 2)} = 28,100$
• Answer: 28,100 books
• Common Mistake: Forgetting to add Week 1's sales to the final total, only giving Week 2's sales.

17. Warehouse Boxes [3 marks]

• Concept: Two-step problem involving subtraction and addition.
• Step 1: Discard damaged boxes. $85,000 - 12,500 = 72,500$
• Step 2: Add new shipment. $72,500 + 20,000 = 92,500$
• Answer: 92,500 boxes
• Marking: 1 mark for correct subtraction, 1 mark for correct addition, 1 mark for final answer with unit.

18. Number Line (a) Value of Point A [1 mark]

• Analysis: The interval from 20,000 to 25,000 is 5,000. There are 10 spaces. Each space = $5,000 \div 10 = 500$.
• Point A is 3 ticks after 20,000. $20,000 + (3 \times 500) = 20,000 + 1,500 = 21,500$
• Answer: 21,500

(b) Value of Point B [1 mark]

• Analysis: Point B is 7 ticks after 25,000. $25,000 + (7 \times 500) = 25,000 + 3,500 = 28,500$
• Answer: 28,500

(c) Difference between B and A [2 marks]

• Working: $28,500 - 21,500 = 7,000$
• Answer: 7,000
• Note: Accept method of counting ticks (10 ticks difference $\times$ 500 = 5,000? No, wait. A is at tick 3, B is at tick 17 relative to start? Let's stick to values. $28,500 - 21,500 = 7,000$).

19. Library Books (a) Books needed [2 marks]

• Concept: Difference between target and current.
• Working: $50,000 - 45,600 = 4,400$
• Answer: 4,400 books

(b) Cost of new books [2 marks]

• Concept: Multiplication.
• Working: $4,400 \times 10 = 44,000$
• Answer: $44,000
• Note: Ensure the dollar sign is included.

20. Museum Visitors (a) Difference between Saturday and Friday [2 marks]

• Working: $18,300 - 12,450$ $18,300 - 12,000 = 6,300$ $6,300 - 450 = 5,850$
• Answer: 5,850 visitors

(b) Round Sunday to nearest thousand [1 mark]

• Analysis: Sunday = 15,250. Look at hundreds digit (2). Since $2 < 5$, round down.
• Answer: 15,000

(c) Total visitors [2 marks]

• Working: $12,450 + 18,300 + 15,250$ Group for easier addition: $12,450 + 15,250 = 27,700$ $27,700 + 18,300 = 46,000$
• Answer: 46,000 visitors
• Marking: 1 mark for correct addition method/intermediate step, 1 mark for final answer.