Idea 15of 24Builds onTens times tens make hundreds
The area model for 23 × 14
How do you multiply two two-digit numbers?
Today you'll discover
- how to split both sides
- the four parts of the rectangle
- how the parts add up
Think firstA rectangle 23 by 14
What is 23 × 14?
Decide first, then press Next. Find all four parts of the rectangle.
A rectangle 23 wide and 14 tall. Dashed lines cut the top into 20 and 3 and the side into 10 and 4, making four parts: 20 × 10 = 200, 20 × 4 = 80, 3 × 10 = 30 and 3 × 4 = 12. Under it, 200 + 80 + 30 + 12 = 322. The last step shows a rectangle 34 by 26.
See the whole ideathe big idea and the key word, in one place
The big idea
Split both factors into tens and ones; the four parts of the rectangle add up to the product.
Easy to get wrongFour parts, not two: 20 × 10 and 3 × 4 alone give 212, and miss the 80 and the 30.
Where it goes nextSeats in rows, tiles on a floor, boxes on a pallet: any rows-of-things problem is an area model.
Key word
- area model
- a rectangle whose sides are the factors, cut into parts; the parts' areas add to the product
Ready to use it?
- Draw an area model for a two-digit multiplication.
- Find and add the four partial products.