Idea 9of 22Builds onScale up: multiply both terms
Scale down: divide both terms
How do you find a smaller ratio that means the same?
Today you'll discover
- how to share both terms into equal groups
- what simplest form is
- why taking away does not work
Think first12 orange and 18 blue
Which smaller ratio means the same as 12 : 18?
Decide first, then press Next. Look for a number both terms share.
A ratio table, orange on top and blue below, starting at 12 and 18. Curved arrows marked divide by 6 over the top and under the bottom; then the table filled, 12 and 18, 6 and 9, 4 and 6, 2 and 3, with the last column ringed and 12 : 18 = 2 : 3 under it. The last step asks about 20 laps run and 15 walked.
See the whole ideathe big idea and the key word, in one place
The big idea
To scale down a ratio, divide both terms by the same number.
Step by step
You can scale down in small steps: 12 : 18, then ÷ 2 to 6 : 9, then ÷ 3 to 2 : 3.
- start12 : 18
- ÷ 26 : 9
- ÷ 32 : 3
Easy to get wrongTake the same amount away from both terms and the ratio changes: 12 : 18 minus 6 each is 6 : 12, which is 1 : 2.
Key words
- scale down
- make an equivalent ratio with smaller terms by dividing both terms by the same number
- simplest form
- a ratio whose terms cannot both be divided by the same whole number again, like 2 : 3
Ready to use it?
- Scale a ratio down by dividing both terms.
- Write a ratio in simplest form.