Lesson 2

Explore

 

In Discover, you examined various referents for some common units for area. In this section you will use these referents and other strategies, like rounding and using grid paper, to estimate the surface area of three-dimensional objects. Creating a net can be extremely helpful for all strategies.

 

Try This 2

 

One method of estimating surface area is drawing the net of the three-dimensional object on grid paper.

1. Trace a net of a toonie on 1-cm Grid Paper. Don’t forget to include the edge of the toonie—it is actually a short cylinder.

2. Look at the net you drew, and count the number of square centimetres it covers to estimate the surface area of the toonie.

3. Use a ruler to measure the diameter and height of the toonie. Check to see how close your estimate is to the actual surface area by using the surface area of a cylinder formula, .

4. What referent could you have used to estimate the surface area of the toonie? How close to the answer in question 3 do you think this estimate would have been?

Share 2

1. Explain why both the values found in questions 2 and 3 could be considered estimates of the surface area of a toonie?
   
   
2. Would square-inch or square-centimetre graph paper help to provide a more accurate estimate of the toonie’s surface area? Explain.

If required, save a copy of your discussion in your course folder.