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Mathematics · Year 3 · Chapter 1

The 2s, 5s and 10s

2 × 5
10
2 × 8
16
2 × 9
18
5 × 4
20
5 × 7
35
5 × 9
45
10 × 6
60
10 × 9
90
7 × 1
7 — one group of 7 is just 7
6 × 0
0 — zero groups means nothing there
2 × 3
6
5 × 2
10
10 × 4
40
2 × 6
12
5 × 5
25
5 × 8
40
2 × 9
18
10 × 7
70
5 × 6
30
2 × 7
14
5 × 9 + 5
50 — that's ten fives
Which is bigger: 2 × 8 or 5 × 3?
2 × 8 = 16 beats 15
10 × 6 − 10
50 — six tens minus one ten is five tens
4 × 5 (hint: turn it around)
20 — same as 5 × 4
0 × 10
0 — zero groups of ten

Multiplying is counting groups

2 × 5 means five groups of two — it counts GROUPS, all the same size. That's why skip counting is the on-ramp: 2, 4, 6, 8, 10 is the 2s table said out loud. The 5s land on 5 and 0, the 10s just put a zero on. Two facts trip almost everyone at first. Seven times ONE is seven — one group of 7 is just the 7, nothing was added (that '×1 means +1' feeling is addition sneaking in where it doesn't belong). And anything times ZERO is zero — zero groups of six lollies is no lollies at all. Multiplying doesn't 'do something' to a number; it says how many groups of it you have.

  • 5 bags × 2 lollies: 2, 4, 6, 8, 10 — ten lollies.
  • 5 × 7 = 35 — seven fives: 5, 10, 15, 20, 25, 30, 35.
  • 7 × 1 = 7. One group of seven. (7 + 1 = 8 is a different question.)
  • 6 × 0 = 0. Zero groups — there's nothing to count.

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