Multi-Digit Multiplication — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
672 × 5 = 3,260 because 2 × 5 = 10, carry the 1, then 7 × 5 = 35 plus 1 = 36, carry the 3, then 6 × 5 = 30 plus 3 = 33.
Corrected: 672 × 5 = 3,360 because 2 × 5 = 10, write 0 carry 1, then 7 × 5 = 35 plus 1 = 36, write 6 carry 3, then 6 × 5 = 30 plus 3 = 33.
The corrected sentence is: "672 × 5 = 3,360 because 2 × 5 = 10, write 0 carry 1, then 7 × 5 = 35 plus 1 = 36, write 6 carry 3, then 6 × 5 = 30 plus 3 = 33.". The original sentence "672 × 5 = 3,260 because 2 × 5 = 10, carry the 1, then 7 × 5 = 35 plus 1 = 36, carry the 3, then 6 × 5 = 30 plus 3 = 33." contained an error that needed to be fixed.
2. Fix the sentence:
2,143 × 3 = 6,329 because 3 × 3 = 9, 4 × 3 = 12, carry the 1, 1 × 3 = 3 plus 1 = 4, 2 × 3 = 6.
Corrected: 2,143 × 3 = 6,429 because 3 × 3 = 9, 4 × 3 = 12 write 2 carry 1, 1 × 3 = 3 plus 1 = 4, 2 × 3 = 6.
The corrected sentence is: "2,143 × 3 = 6,429 because 3 × 3 = 9, 4 × 3 = 12 write 2 carry 1, 1 × 3 = 3 plus 1 = 4, 2 × 3 = 6.". The original sentence "2,143 × 3 = 6,329 because 3 × 3 = 9, 4 × 3 = 12, carry the 1, 1 × 3 = 3 plus 1 = 4, 2 × 3 = 6." contained an error that needed to be fixed.
3. Fix the sentence:
509 × 8 = 4,062 because 9 × 8 = 72, carry the 7, then 0 × 8 = 0 plus 7 = 7, then 5 × 8 = 40.
Corrected: 509 × 8 = 4,072 because 9 × 8 = 72, write 2 carry 7, then 0 × 8 = 0 plus 7 = 7, then 5 × 8 = 40.
The corrected sentence is: "509 × 8 = 4,072 because 9 × 8 = 72, write 2 carry 7, then 0 × 8 = 0 plus 7 = 7, then 5 × 8 = 40.". The original sentence "509 × 8 = 4,062 because 9 × 8 = 72, carry the 7, then 0 × 8 = 0 plus 7 = 7, then 5 × 8 = 40." contained an error that needed to be fixed.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. 1,325 × 4 = 5,300
5×4=20 (write 0, carry 2); 2×4+2=10 (write 0, carry 1); 3×4+1=13 (write 3, carry 1); 1×4+1=5. Product = 5,300.
2. 847 × 6 = 5,082
7×6=42 (write 2, carry 4); 4×6+4=28 (write 8, carry 2); 8×6+2=50. Product = 5,082.
3. 2,006 × 3 = 6,018
6×3=18 (write 8, carry 1); 0×3+1=1; 0×3=0; 2×3=6. Product = 6,018.
4. When multiplying a number by 0, the product is always zero.
Any number × 0 = 0. This is the zero property of multiplication.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Why is it important to line up digits by place value when multiplying?
Sample answer: Lining up digits by place value keeps ones, tens, hundreds, and thousands in the correct columns so carried numbers are added to the right place.
Misaligning place values leads to incorrect products because partial products must be combined at the correct positions.
2. A school orders 1,250 pencils for each of 4 classrooms. How many pencils are ordered in total?
Sample answer: 1,250 × 4 = 5,000. The school orders 5,000 pencils in total.
1,250 × 4 = 5,000. (0×4=0; 5×4=20 carry 2; 2×4+2=10 carry 1; 1×4+1=5.)