Ratios and Proportion
A ratio compares two or more quantities. Ratios and proportions are used in recipes, maps, and sharing problems to describe how amounts relate to each other.
What You Need to Know
Key Concept Diagram
A ratio compares quantities: 3:2 means 3 parts to 2 parts (5 parts total)
Equivalent ratios are found by multiplying or dividing both parts by the same number: 2:3 = 4:6 = 6:9
To share an amount in a given ratio: find the total parts, find one part, then multiply
Scale factors in maps and models use ratios: a scale of 1:100 means 1 cm represents 100 cm
Key Vocabulary
Ratio
A comparison of two or more quantities using division, written as a:b
Proportion
An equation stating that two ratios are equal
Equivalent ratio
A ratio that represents the same relationship as another, found by scaling
Scale factor
The ratio used to enlarge or reduce a shape or model
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
Simplify the ratio 12:8.
Question 2
Share $60 in the ratio 2:3.
Question 3
A recipe uses flour and sugar in the ratio 5:2. If there is 200g of flour, how much sugar is needed?
Key Concepts Summary
- ●A ratio compares quantities: 3:2 means 3 parts to 2 parts (5 parts total)
- ●Equivalent ratios are found by multiplying or dividing both parts by the same number: 2:3 = 4:6 = 6:9
- ●To share an amount in a given ratio: find the total parts, find one part, then multiply
- ●Scale factors in maps and models use ratios: a scale of 1:100 means 1 cm represents 100 cm