Idea 13of 22Builds onFind a missing term
Add two columns to make a third
How can two columns of a ratio table make a new one?
Today you'll discover
- why groups add up
- why both rows are added
- how to check with a scale factor
Think first2 : 3 and 8 : 12 are in the table
1 group is 2 : 3 and 4 groups are 8 : 12. What are 5 groups?
Decide first, then press Next. Add the top numbers, then the bottom numbers.
A ratio table, orange on top and blue below, with columns 2 and 3, 8 and 12, and a blank column. Then the table filled with 10 and 15 and the line 2 : 3 plus 8 : 12 equals 10 : 15 under it. Then arrows times 5 from the first column to the last, which is ringed. The last step shows red and white beads: 3 and 4, 6 and 8, 30 and 40, and a blank.
See the whole ideathe big idea and the key word, in one place
The big idea
Adding two columns of a ratio table, top and bottom, makes another equivalent ratio.
Halve, tooA column can be halved as well: half of 8 : 12 is 4 : 6, which is 2 groups.
Easy to get wrongAdd both rows, never just one. 2 : 3 plus 8 : 12 is 10 : 15, not 10 : 12.
Key word
- combining columns
- adding two columns of a ratio table, top to top and bottom to bottom, to make a new column
Ready to use it?
- Add two columns of a ratio table.
- Halve a column to find a smaller one.