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Part 5:
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Ratio and Proportion |
| Calculating with Ratios (1) Suppose we read that, to make up an orange drink, we must mix orange concentrate with water in the ratio 1 : 4. This means we need 1 measure of concentrate to 4 measures of water (not the other way round, the order of the words and numbers is extremely important). The measures can be spoons, cups or buckets, it doesn't matter as long as they are all the same. 1 measure of concentrate plus 4 measures of water equals 5 measures altogether. So the concentrate forms 1/5 of the total and the water forms 4/5 of the total. Here is another example. A concrete mix requires sand, cement and gravel in the ratio:- 3 : 5 : 2. This means we need 3 buckets of sand, 5 buckets of cement and 2 buckets of gravel, in that order, making 10 buckets in all as one 'batch'. Sand forms 3/10 of the total, cement forms 5/10 of the total and gravel forms 2/10 of the total. As you see, we will be using fractions a lot to solve problems involving ratios. Because ratios are really just fractions under another name. |
