What is a ratio?
Ratios are usually written in the form a:b. The numbers are in direct proportion when they increase or decrease in the same ratio.
Example
A fraction compares a part to a whole; a ratio compares a part to a part. For example, here, the ratio would be 3:1.
Simplifying ratios
Because all numbers in a ratio are in direct proportion, some ratios can be made simplified by dividing all numbers in the ratio by the same integer. For example, 2:4 would be simplified to 1:2 by dividing 2 and 4 by 2. Both of these ratios are the same!
Sharing
Ratios, like fractions, can be used to share or divide amounts. Here is my example. A and B share £500 in the ratio 2:3. How much do each get?
To find the answer, we add both sides of the ratio to find how many blocks to put in our bar model. There are 5 blocks, each worth £100. If fractions were used, the denominator would also be 5. To find out how much A gets, multiply 2 by 100. To find out how much B gets, multiply 3 by 100.
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Maths Revision
RandomMy funny and well-explained KS3 Maths Revision guide, derived from Bitesize. Still in progress, as I learn the nightmare called Maths by myself.
