Ratios
4.1 Writing Ratios
4.2 Simplifying Ratios
4.3 Unit Ratios and Scale Factors
4.4 Using Ratios To Find Amounts
4.5 Scale Drawings
4.6 Sharing a Ratio
4.7 Rates
E.g. red squares to blue squares
= 3:5
Just like when you simplify a fraction
E.g. 2:4
= 1:2
E.g. 2 cm: 4 mm
Find a common unit
= 20 mm: 4 mm
Then drop the units
= 20:4
If it is a fraction- just simplify it like normal
E.g. 1 3/4: 2/4
= 7/4: 2/4
A unit ratio is...
When you have a ratio and you need one of the numbers to be 1 so you can create the ratio with any quantity. You need to use the smaller number and divide it by itself to get 1. What you do to one side you must do to the other so divide the other side by the smaller number to get your unit ratio.
E.g. 34:19
Divide by 19 on both sides
= 1.79:1
To share a ratio, add the numbers in the ratio together, then divide them by the number you have to share it into. Then multiply the numbers in the ratio by the answer of the previous step.
E.g. 30 (2:3)
30/5 = 6
2x6= 12
3x6= 18
12:18
E.g. 21:g = 7:3
Put the ratios on top of one another (it doesn't matter the order- which ever makes more sense). What is the relation between the numbers? In this example, 7 was multiplied by 3 to get 21. To solve the problem, the other number, 3, has to be multiplied by 3 to work out the value of g.
g= 9
Picture:Real life
In maps and drawings, it is hard to draw the item to scale (the size it is in real life). Because of this, you need a scale.
E.g. 1m:1cm
A rate includes per. An example is 60km/h
To calculate the average speed based off a rate, change the rate into a unit ratio. 