## Diagrams and Sketches

Some problems involve the determination of a quantity of items, such as the number of nails per sheet of plywood or the number of studs in a wall. In solving these types of problems it usually is helpful to draw a sketch or a diagram.

Problem: How many posts are needed to build a fence 100 ft long with posts 10 ft apart?

Solution: For many people the first response would be 10:

100 ft

10.0 ft/post but a diagram, Figure 1.1 shows that the correct number of posts is 11.

This is an example of a situation where a wrong answer is possible if you do not interpret the problem correctly. In this example, 10 is the number of spaces, not the number of posts.

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