Lesson 2 of 15
What 3 : 2 says, and what it does not
Show on a big screenA class has 30 learners. 18 are girls. What is the ratio of girls to boys?
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Step 1 of 3
- Thirty seats, one bar.
- Eighteen are girls: 18 : 12.
- Same bar, out of 30: 18 : 30 = 3 : 5.
The rule
Girls to boys is 3 : 2.
A ratio a : b says this. For every a of the first, there are b of the second. Here a and b are numbers.
- There are 30 − 18 = 12 boys. Girls to boys is 18 : 12. Divide both by 6 to get 3 : 2.
- Girls to the class is 18 : 30. Divide both by 6 to get 3 : 5.
- Boys to girls is 12 : 18, or 2 : 3. Order matters: the first name comes first.
3 : 2 names five parts. Three are girls' parts. Two are boys' parts.
Try the lab to finish this lesson.