Page 100 - Knowledge Organiser Yr8 24-25

Knowledge Base: Mathematics TOPIC 19: Ratio Year 8 | Spring Term 2
By the end of this topic you should be able to:
• Simplify a ratio
• Find equivalent amounts given a ratio
• Convert between ratio and proportion
• Divide into a given ratio
• Use ratios to solve problems
• Write ratio in the 1:n form
• Work with scale factors
Language
Meaning
Example
Proportion
Compares a part to the whole and can be written as a fraction
Ratio
Compares 2 or more parts. You write a ratio using a colon :
Divide in a ratio
To share out a quantity into a number of (usually) unequal parts
£60 divided in the ratio 2 : 1 is £40 : £20
Simplify a ratio
To write a ratio in its simplest form by dividing by common factor
28 : 14 can be simplified to 2 : 1 by dividing both parts by the common factor 14
1:n
A ratio that has been simplified so that its first number is 1
4 : 10 can be divided by 4 to give the equivalent ratio 1 : 2.5
Scale factor
The ratio length of one image : length of object
A scale factor of 3 means all the lengths
in the image are 3 times those of the object
Important things to remember:
Ratio compares the size of parts
Proportion compares the size of a part with the whole
Worked examples
100