Teaching mathematics
Teaching mathematics

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Teaching mathematics

3.2 Connecting ratio and proportion

Throughout this week you have looked at various applications of proportional reasoning. Finally, you will look at how notation for ratio and proportion are linked.

Recapping what was discussed at the start of this section, a ratio represents a relationship between two quantities. A proportion represents one quantity in relation to the whole.

For example, a tropical drink uses 150 ml of orange juice and 100 ml of mango juice.

The ratio of orange to mango, in the simplest form, is 3:2, as for every 3 parts of orange juice, 2 parts of mango juice is needed.

Expressed as a fraction, the proportion of orange juice in the drink is

three divided by five

as there are 5 parts in total and 3 of these are orange juice.

Activity 19 Matching ratio and proportion

Timing: Allow 10 minutes

For each of the sets of counters displayed, write the ratio and proportion in the box below.

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Answer

Ratio of red to blue is 3:1

The proportion of red is three divided by four

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Answer

Ratio of red to blue is 1:2

The proportion of red is one divided by three

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Answer

Ratio of red to blue is 4:5

The proportion of red is four divided by nine

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Answer

Ratio of red to blue is 2:3

The proportion of red is two divided by five

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Answer

Ratio of red to blue is 1:1

The proportion of red is one divided by two

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Answer

Ratio of red to blue is 3:1

The proportion of red is three divided by four

TM_1

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