Multiplying and dividing in your head

Mathematics · Multiplication & Division · ages 8-9

Name ______________________ Date ____________

What is 1 × 35?
- 1
- 35
- 36
What is 9 x 1?
- 9
- 0
- 1
- 10
What is 7 x 0?
- 0
- 7
- 70
- 1
What is 6 × 0?
- 0
- 6
- 60
What is 30 x 4?
- 120
- 12
- 1200
- 34
What is 100 ÷ 100?
- 0
- 1
- 100
Work out 2 x 7 x 5 by choosing a useful pair first.
Answer: ______________
What is 2 × 7 × 5? Look for an easy pair to multiply first.
- 70
- 35
- 14
Maya says '9 × 0 = 9, because the 9 does not change.' What did Maya mix up?
- She used the rule for × 1 instead of the rule for × 0
- She forgot to multiply by 10
- She added 9 and 0 instead of multiplying
Work out 4 × 9 × 5 in your head. Which pair should you multiply first to make it easiest?
- 4 × 9, because it comes first
- 9 × 5, because it is the biggest pair
- 4 × 5, because it makes a friendly 20

Answer key

For grown-ups. Fold this page away before handing over the rest.

35 · Multiplying by 1 does not change a number. One group of 35 is still 35.
9 · Multiplying by 1 leaves the number unchanged: 9.
0 · Any number times 0 is 0.
0 · Any number times 0 is 0. There are zero groups, so there is nothing there.
120 · 3 tens times 4 is 12 tens: 120.
1 · Any number divided by itself is 1, just like any number times 1 stays the same.
70 · Pair 2 x 5 = 10 first, then 10 x 7 = 70.
70 · 2 × 5 = 10 is an easy pair. Then 10 × 7 = 70.
She used the rule for × 1 instead of the rule for × 0 · × 1 keeps a number the same, but × 0 always makes 0. Maya used the wrong rule.
4 × 5, because it makes a friendly 20 · 4 × 5 = 20, a friendly number. Then 20 × 9 = 180.