Idea 5of 24Builds onDouble, then double again
Split a fact into two you know
How can two easy facts make a hard one?
Today you'll discover
- how to cut an array into two parts
- which facts to pick
- why the parts add up
Think first7 rows of 8: a hard fact
Which two facts you know add up to 7 × 8?
Decide first, then press Next. Look for a cut that leaves two easy facts.
7 rows of 8 dots. A dashed line cuts it after 5 rows: the top 5 rows orange, 5 × 8 = 40; the bottom 2 rows blue, 2 × 8 = 16. Then 40 + 16 gives 7 × 8 = 56. The last step shows 12 rows of 6.
See the whole ideathe big idea and the key word, in one place
The big idea
Split a fact into two facts you know, then add the two products.
Split, multiply, add
One hard fact becomes two easy ones.
- 5 × 840
- 2 × 816
- 7 × 856
Easy to get wrongSplit only one factor, and its parts must add back to it: 5 + 2 = 7.
Key word
- distributive property
- splitting one factor into parts, multiplying each part, then adding: 7 × 8 = 5 × 8 + 2 × 8
Ready to use it?
- Split a fact into two facts you know.
- Find a 7s or 12s fact from 5s, 2s and 10s.