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Teaching mathematics
Teaching mathematics

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3.1 Using simple ratios to make comparisons

First, look at Figures 20–22 and then do the activity based on them.

Using Cuisenaire rods to represent ratios
Figure 20 Using Cuisenaire rods to represent ratios
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Some Cuisenaire rods: ten small red rods and four longer yellow rods

Figure 20 Using Cuisenaire rods to represent ratios
Using Cuisenaire rods to compare the ratio of lengths
Figure 21 Using Cuisenaire rods to compare the ratio of lengths
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Some Cuisenaire rods: one white cube rod (with length 1) and one green rectangular rod (with length 3)

Figure 21 Using Cuisenaire rods to compare the ratio of lengths
Using multilink cubes to represent ratios
Figure 22 Using multilink cubes to represent ratios
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Some cubes: eight white cubes and twelve orange cubes

Figure 22 Using multilink cubes to represent ratios

Activity 18 Writing ratios

Timing: Allow 5 minutes

Write the ratios for each of the images shown above in the simplest form.

  • a.What is the ratio of red rods to yellow rods?
  • b.What is the ratio of the lengths of the green and white rods?
  • c.What is the ratio of orange to white cubes?

Discussion

  • a.10:4 which simplifies to 5:2.
  • b.3:1.
  • c.12:8 which simplifies to 3:2.