Introduction to Ratio
A ratio compares two or more quantities of the same kind, showing how many times one quantity contains or is contained by another.
What You Need to Know
Key Concept Diagram
A ratio is written as a:b (e.g. 2:3) meaning for every 2 of one thing there are 3 of another
Ratios can be simplified just like fractions by dividing both numbers by their common factor
Equivalent ratios have the same relationship between their parts (e.g. 2:3 = 4:6 = 10:15)
Part-to-whole reasoning: in a 2:3 ratio, the whole is 5 parts and one part is 2/5 of the total
Key Vocabulary
Ratio
A comparison of two or more quantities, written using a colon (e.g. 3:5)
Equivalent ratio
Ratios that represent the same relationship (e.g. 1:2 and 3:6)
Simplest form
A ratio where the numbers share no common factor other than 1
Part-to-whole
A comparison of one part to the total amount of all parts combined
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
In a bag of 10 marbles, 4 are red and 6 are blue. What is the ratio of red to blue marbles?
Question 2
Simplify the ratio 12:18.
Question 3
Orange juice is mixed with water in a ratio of 1:3. How much water is needed for 2 cups of orange juice?
Key Concepts Summary
- ●A ratio is written as a:b (e.g. 2:3) meaning for every 2 of one thing there are 3 of another
- ●Ratios can be simplified just like fractions by dividing both numbers by their common factor
- ●Equivalent ratios have the same relationship between their parts (e.g. 2:3 = 4:6 = 10:15)
- ●Part-to-whole reasoning: in a 2:3 ratio, the whole is 5 parts and one part is 2/5 of the total