Multiplication

Advanced Math 4 · Unit 4 · multi-digit-multiplication · Teacher edition

multi-digit-multiplication

Name ______________________________Date ______________

1.
Compute $308 \times 7$ .
Answer: ______________
2.
A library has $24$ shelves. Each shelf holds $36$ books. There are already $250$ books on the shelves. How many more books can fit?
Answer: ______________
3.
Ben works out $34 \times 26$ like this: $34 \times 6 = 204$ , then $34 \times 2 = 68$ , then $204 + 68 = 272$ . His teacher says the answer is wrong. What is the correct product?
1. (A)
  $272$
2. (B)
  $804$
3. (C)
  $900$
4. (D)
  $884$

Answer key — Multiplication

1.
2156multi-digit-multiplication-01
$308 \times 7 = 300 \times 7 + 8 \times 7 = 2{,}100 + 56 = \mathbf{2{,}156}$ .
2.
614multi-digit-multiplication-02
Capacity: $24 \times 36 = 600 + 120 + 120 + 24 = 864$ . Books that still fit: $864 - 250 = \mathbf{614}$ . Estimate check: $25 \times 36 = 900$ , and $900 - 250 = 650$ , close to $614$ .
3.
(D)
$884$
multi-digit-multiplication-03
$34 \times 26 = 34 \times 6 + 34 \times 20 = 204 + 680 = \mathbf{884}$ . ( $272$ uses $68$ instead of $680$ — the partial product landed in the wrong place; $804$ drops the $4 \times 20$ box of the area model; $900$ is only the estimate.)