Primary 4 Mathematics · Chapter 3 · Answers and explanations

Lesson 3.2: Multiplication of 4-Digit Numbers (answers)

Section A · Multiple choice 4 marks

1. What is 2,345 × 4?1 mark

(A) 8,260(B) 10,380(C) 9,380(D) 9,280

Answer: (C) 9,380Ones: 5 × 4 = 20, write 0 and regroup 2 tens. Tens: 4 × 4 + 2 = 18, write 8 and regroup 1 hundreds. Hundreds: 3 × 4 + 1 = 13, write 3 and regroup 1 thousands. Thousands: 2 × 4 + 1 = 9, write 9. So 2,345 × 4 = 9,380.

2. What is 3,068 × 5?1 mark

(A) 15,000(B) 15,040(C) 16,340(D) 15,340

Answer: (D) 15,340Ones: 8 × 5 = 40, write 0 and regroup 4 tens. Tens: 6 × 5 + 4 = 34, write 4 and regroup 3 hundreds. Hundreds: 0 × 5 + 3 = 3, write 3. Thousands: 3 × 5 = 15, write 15. So 3,068 × 5 = 15,340.

3. What is 4,005 × 7?1 mark

(A) 28,035(B) 28,005(C) 24,535(D) 280,350

Answer: (A) 28,035Ones: 5 × 7 = 35, write 5 and regroup 3 tens. Tens: 0 × 7 + 3 = 3, write 3. Hundreds: 0 × 7 = 0, write 0. Thousands: 4 × 7 = 28, write 28. So 4,005 × 7 = 28,035.

4. Round 2,987 to the nearest thousand to estimate 2,987 × 4. What is the estimate?1 mark

(A) 8,000(B) 12,000(C) 16,000(D) 1,200

Answer: (B) 12,0002,987 is close to 3,000. Estimate: 3,000 × 4 = 12,000. (Wrong answers come from rounding down to 2,000, rounding up to 4,000, or losing zeros.)

Section B · Write your answer 11 marks

5. What is 1,526 × 6?1 mark

Answer: 9,156Ones: 6 × 6 = 36, write 6 and regroup 3 tens. Tens: 2 × 6 + 3 = 15, write 5 and regroup 1 hundreds. Hundreds: 5 × 6 + 1 = 31, write 1 and regroup 3 thousands. Thousands: 1 × 6 + 3 = 9, write 9. So 1,526 × 6 = 9,156.

6. What is 5,208 × 3?1 mark

Answer: 15,624Ones: 8 × 3 = 24, write 4 and regroup 2 tens. Tens: 0 × 3 + 2 = 2, write 2. Hundreds: 2 × 3 = 6, write 6. Thousands: 5 × 3 = 15, write 15. So 5,208 × 3 = 15,624.

7. Round 4,078 to the nearest thousand to estimate 4,078 × 5. What is the estimate?1 mark

Answer: 20,0004,078 is close to 4,000. Estimate: 4,000 × 5 = 20,000. (The exact answer is 20,390, so the estimate is close.)

8. What is 7,040 × 8?1 mark

Answer: 56,320Ones: 0 × 8 = 0, write 0. Tens: 4 × 8 = 32, write 2 and regroup 3 hundreds. Hundreds: 0 × 8 + 3 = 3, write 3. Thousands: 7 × 8 = 56, write 56. So 7,040 × 8 = 56,320.

9. What is the product of 9,999 and 2?1 mark

Answer: 19,998Ones: 9 × 2 = 18, write 8 and regroup 1 tens. Tens: 9 × 2 + 1 = 19, write 9 and regroup 1 hundreds. Hundreds: 9 × 2 + 1 = 19, write 9 and regroup 1 thousands. Thousands: 9 × 2 + 1 = 19, write 19. So 9,999 × 2 = 19,998.

10. A factory makes 1,740 toys every day. Round 1,740 to the nearest thousand to estimate the toys made in 6 days. Then find the exact number.2 marks

Answer: Estimate 12,000; exact 10,4401,740 rounds to 2,000. Estimate: 2,000 × 6 = 12,000. Exact: Ones: 0 × 6 = 0, write 0. Tens: 4 × 6 = 24, write 4 and regroup 2 hundreds. Hundreds: 7 × 6 + 2 = 44, write 4 and regroup 4 thousands. Thousands: 1 × 6 + 4 = 10, write 10. So 1,740 × 6 = 10,440. The estimate is a little higher because we rounded up.

11. A stadium has 8 blocks. Each block has 1,250 seats. 3,764 seats are taken. How many seats are empty?2 marks

Answer: 6,236All seats: 1,250 × 8 = 10,000 (0 × 8 = 0; 5 × 8 = 40, write 0 regroup 4; 2 × 8 + 4 = 20; 1 × 8 + 2 = 10). Empty seats: 10,000 − 3,764 = 6,236.

12. A shop had 10,000 eggs. It sold 2,375 eggs each day for 4 days. How many eggs are left?2 marks

Answer: 500Eggs sold: 2,375 × 4 = 9,500 (5 × 4 = 20, write 0 regroup 2; 7 × 4 + 2 = 30, write 0 regroup 3; 3 × 4 + 3 = 15, write 5 regroup 1; 2 × 4 + 1 = 9). Eggs left: 10,000 − 9,500 = 500.

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