Multiplication (multi-digit)

Advanced Math 5 · Unit 4 · multi-digit-multiplication-5 · Teacher edition

multi-digit-multiplication-5

Name ______________________________Date ______________

1.
Compute $48 \times 25$ .
Answer: ______________
2.
A school orders $148$ boxes of pencils. Each box holds $25$ pencils. The school hands out one pencil to each of its $3{,}512$ students. How many pencils are left over?
Answer: ______________
3.
Which is the product $312 \times 204$ ?
1. (A)
  $63{,}648$
2. (B)
  $7{,}488$
3. (C)
  $62{,}400$
4. (D)
  $64{,}848$

Answer key — Multiplication (multi-digit)

1.
1200multi-digit-multiplication-5-01
$48 \times 25 = 12 \times (4 \times 25) = 12 \times 100 = \mathbf{1{,}200}$ .
2.
188multi-digit-multiplication-5-02
$148 \times 25 = 100 \times 25 + 48 \times 25 = 2{,}500 + 1{,}200 = 3{,}700$ . Left over: $3{,}700 - 3{,}512 = \mathbf{188}$ .
3.
(A)
$63{,}648$
multi-digit-multiplication-5-03
$312 \times 204 = 312 \times 200 + 312 \times 4 = 62{,}400 + 1{,}248 = \mathbf{63{,}648}$ . ( $7{,}488$ is $312 \times 24$ — the zero in $204$ was dropped, and the four-digit size should have been the warning; $62{,}400$ forgets the $\times 4$ part; $64{,}848$ adds $312 \times 8$ instead of $312 \times 4$ .)