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Ratios and Proportions
Learn how to share quantities in a given ratio and solve problems involving direct proportion.
Key Ideas
- A ratio compares values, telling us how much of one thing there is compared to another.
- The order of the numbers in a ratio matters.
- To share a quantity in a ratio a:b, first find the total number of parts (a + b), then divide the total quantity by this number to find the value of one part.
- Direct proportion means as one value increases, the other increases at the same rate.
Worked Examples
Example 1
Share $60 in the ratio 2:3.
Explanation
Total parts = 2 + 3 = 5 parts.
Value of one part = $60 ÷ 5 = $12.
First share = 2 parts × $12 = $24.
Second share = 3 parts × $12 = $36.
Check: $24 + $36 = $60.
Ready to Practice?
Common Mistakes
- ×Dividing by one of the ratio numbers instead of the total number of parts.
- ×Writing the answer in the wrong order.
Exam Tip
"Always check if your final answers add up to the original total amount."