05-NelsonMathGr6-Chap05 7/18/05 4:39 PM Page 142

CHAPTER 5 1 Measuring Length

Goal Select an appropriate measuring unit.

James’s family went to Lighthouse Park in West Vancouver. The park has many very old and tall fir, cedar, and arbutus trees. James tried to decide which unit he would use to measure the trip and everything he saw. He thinks he can use decametres to measure the length of a path around the base of this tree.

? What units of length are appropriate for describing their trip?

decametre (dam) James’s Comparison A unit of measurement for length 1 dam 10 m Dad stood next to a young tree that is just about as tall as he is. Dad’s height is 195 cm.

A. What unit would you use to describe the height of the older trees in the park? Explain your choice. B. What unit would you use to describe the distance James’s family travelled to get to Lighthouse Park? Why? C. James picked up a piece of bark from a fallen arbutus tree. The bark is known for being very thin. What unit would you use to describe its thickness? D. What unit would you use to describe the thickness of a cedar leaf? E. What other things in a West Coast rain forest might be measured in the same units as your answer to Part D?

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05-NelsonMathGr6-Chap05 7/18/05 4:39 PM Page 143 Reflecting

1. Why did all of the units you chose include “metre”? 2. Suppose a leaf was 7.2 cm long. Why can you say that it had been measured to the nearest millimetre? 3. Why are different units appropriate for different measurements?

Checking 4. Select an appropriate unit for each measurement. Explain each choice. a) the height of a room b) the thickness of a window c) the distance across your town or city Practising 5. A nursery is selling young trees. What units are appropriate for these measurements? Explain. a) the heights of the trees b) the lengths of the leaves of the trees 6. For which measurements are centimetres appropriate? Explain. a) the thickness of your math book b) the thickness of your fingernail c) the thickness of 100 sheets of paper 7. Why might you measure the thickness of a wire in millimetres rather than centimetres? 8. Ryan is in a video store. What items in the store, if any, might be measured in these units? a) millimetres c) metres b) centimetres d) kilometres 9. Is it likely that a tall building would be measured in kilometres? Explain. 10. A decimetre is 0.1 metre. A decametre is 10 m. What might be the name of the unit between decametres and kilometres? Explain.

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