1. Chapter 10
Ratio

2. Learning Objectives Find equivalent ratios Simplify ratios
Sharing a quantity in a ratio
Direct proportion

3. Ratio Ratio is a way of dividing things up Example
Give the ratio of sweets to chocolates to sweets

4. Equivalent Ratio You must multiply all terms by the same number
Examples
Find 3 equivalent ratios to 3:4
The ratio of boys to girls in a school is 3:4. If there are 72 boys:
(a) how many girls are there?
(b) how many pupils are there in the school in total?

5. Simplifying Ratio
Divide each term by the biggest number that goes into all terms evenly
Example
Simplify:
(a) 15:9
(b) 6:12:24
(c) 2cm:50mm
(d) 3cm2:75cm2

6. Sharing in a Given Ratio
Add up all the parts of the ratio to give the total parts
Divide the quantity by the total number of parts to give what 1 part is worth
Multiply by the number of parts in each term
Examples
1. Divide £57.75 in the ratio 5:6

7. More Ratio Examples
2. A box contains red, green and brown buttons in the ratio 1:2:5. There are 104 buttons in the box. How many are there of each colour?

8. Proportion Always find what 1 is worth Examples
4 cakes cost £1.20. How much would 6 cakes cost?
These are the ingredients for 12 rock cakes. How much of each ingredient would you need for 20 rock cakes?
240g flour
75g margarine
125g sugar
150g fruit
¼ teaspoon spice