Teaching Notes

You can help your students grasp the parallax problem by having students stand at two adjacent corners of the room and point at an object on the opposite wall. Ask students to walk to that wall and identify the object. Ask how they could identify the object if they could not walk to the wall (by making a drawing). Ask how to find the angles (tracing the angles on the floor and measuring them with a protractor).

You might select four different objects, one on each wall, and assign each object to several groups, to keep the students separated.

The scale drawing involves ratio and proportion, a difficult topic for many students. The students must figure out what scale to use on their graph paper. As the Student Book suggests, it can be helpful to make a rough sketch of the triangle. If they label the baseline, whose length they have already measured, they know one length that must fit on their paper. From that length, they can estimate the unknown distance. You can help by suggesting possible scales. You can say, “How would it work if five boxes on the graph paper represented 10 m?” (but don’t give them the answer). If they can explain why a particular proposed scale will not work, they are probably able to choose an appropriate scale and make the drawing.