Multi-Digit Multiplication — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. Using partial products, 68 × 24 = 68 × 4 + 68 × 20 = 272 + 1,360 = 1,632
Add the two partial products: 272 + 1,360 = 1,632. You can verify by checking that 68 × 4 = 272 and 68 × 20 = 1,360.
2. In the area model for 35 × 16, the four rectangles are 30 × 10 = 300, 30 × 6 = 180, 5 × 10 = 50, and 5 × 6 = 30
The area model splits 35 into 30 + 5 and 16 into 10 + 6, making four rectangles. The last one is 5 × 6 = 30. All four add up to 300 + 180 + 50 + 30 = 560.
3. 42 × 37 = 1,554
Using partial products: 42 × 7 = 294 and 42 × 30 = 1,260. Adding them gives 294 + 1,260 = 1,554.
4. The first partial product of 84 × 19 is 84 × 9 = 756
The first partial product multiplies 84 by the ones digit of 19. Since 84 × 9 = 756, that is the value of the first partial product.
5. The second partial product of 84 × 19 is 84 × 10 = 840
The second partial product multiplies 84 by the tens digit value of 19, which is 10. So 84 × 10 = 840. Adding both partial products: 756 + 840 = 1,596.
6. 57 × 46 = 2,622
Using partial products: 57 × 6 = 342 and 57 × 40 = 2,280. Adding them gives 342 + 2,280 = 2,622.
7. A garden has 23 rows with 41 plants in each row. The garden has 943 plants.
Multiply 23 × 41 to find the total: 23 × 1 = 23 and 23 × 40 = 920, so 23 + 920 = 943 plants in the garden.
8. Estimate 77 × 34 by rounding: 80 × 30 = 2,400
Round 77 up to 80 and 34 down to 30 to get an estimate. 80 × 30 = 2,400, which is close to the exact answer of 2,618.
9. 66 × 28 = 1,848
Using partial products: 66 × 8 = 528 and 66 × 20 = 1,320. Adding them gives 528 + 1,320 = 1,848.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
39 × 17
→ 663
936
54 × 26
→ 1,404
935
72 × 13
→ 936
1,404
85 × 11
→ 935
663
Use partial products to verify each: 39 × 17 = 39 × 7 + 39 × 10 = 273 + 390 = 663; 54 × 26 = 1,404; 72 × 13 = 936; 85 × 11 = 935.