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Part 5:
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Ratio and Proportion |
| Proportion If two quantites both increase or both decrease together at the same rate, or in the same ratio, we say that they are in direct proportion. For example, if you double one you double the other: 5 boxes cost £7 so 10 boxes of the same type cost £14. If, as one quantity increases, the other decreases in the same ratio, we say that they are in inverse proportion. For example, if you double one you halve the other: a 400 watt microwave takes 10 minutes so an 800 watt microwave will take 5 minutes to cook the same food. To solve problems involving these we will have to use the method called the unitary method. (There are other methods too). We won't worry too much about the words direct or inverse, simply whether the number we are looking for is larger or smaller than before. |
