The tip
A ratio like 3:5 means 3 + 5 = 8 equal parts. Divide the total by the number of parts, then multiply by the part you want.
Try it
The ratio of boys to girls in a class of 40 students is 3:5. How many girls are in the class?
- A15
- B20
- C24
- D25
Reveal answer
Answer: D. 25
There are 3 + 5 = 8 parts, so each part is 40 / 8 = 5 students. Girls are 5 parts: 5 x 5 = 25. Boys are 3 x 5 = 15, and 15 + 25 = 40.
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