Idea 2of 22Builds onA ratio compares two amounts
Part to part
How do you compare one part of a set with another part?
Today you'll discover
- what a part of a set is
- which number goes first
- how to compare the two parts either way
Think first3 orange and 5 blue on one tray
What is the ratio of orange counters to blue counters?
Decide first, then press Next. Read which colour the question names first.
3 orange circles and 5 blue squares on a tray, with the line orange to blue equals 3 to 5; then the line blue to orange equals 5 to 3 under it. Then a tray of 6 orange and 9 blue. The last step shows 5 orange and 2 blue.
See the whole ideathe big idea and the key word, in one place
The big idea
A part-to-part ratio compares one part of a set with another part.
In a class12 girls and 10 boys: girls to boys is 12 : 10. Both numbers are parts of the class.
Easy to get wrongA part-to-part ratio never uses the total. With 3 orange and 5 blue, orange to blue is 3 : 5, not 3 : 8.
Key word
- part-to-part ratio
- a ratio that compares one part of a set with another part, like orange counters to blue counters
Ready to use it?
- Write a part-to-part ratio for two colours.
- Write the same two parts in the other order.