Idea 14of 24Builds onSplit a fact into two you know
Tens times tens make hundreds
What is 30 × 20, and why?
Today you'll discover
- how a rectangle cuts into hundred squares
- why the zeros come
- how a fact you know helps
Think firstA rectangle 30 by 20
What is 30 × 20?
Decide first, then press Next. Count the squares of 100.
A rectangle 30 wide and 20 tall. Dashed squares 10 by 10 appear inside it, 3 across and 2 down, each marked 100. Then 30 × 20 = 600 is written inside. The last step shows a rectangle 40 by 30.
See the whole ideathe big idea and the key word, in one place
The big idea
Tens times tens makes hundreds: 30 × 20 is 3 × 2 hundreds, 600.
From a fact to hundreds
One fact, three sizes.
- 3 × 26
- 30 × 260
- 30 × 20600
Easy to get wrongCount hundreds, not just zeros: 40 × 50 = 2000, because 4 × 5 = 20 hundreds.
Key word
- hundred square
- a square 10 by 10: its area is 10 × 10 = 100
Ready to use it?
- Multiply two multiples of ten in your head.
- Explain why tens times tens makes hundreds.