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Home > CCA > Chapter 9 > Lesson 9.1.4 > Problem 9-40

9-40.

Find a rule that represents the number of tiles in Figure for the tile pattern below.  

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Figure 1

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Figure 2

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Figure 3

The single unit tile is circled in red. The middle 2 by 3 rectangle is circled in green. The one unit tile on the bottom right is circled in blue.
Figure 1

The single unit tile is circled in red. The middle 3 by 4 rectangle is circled in green. The 2 unit tiles on the bottom right are circled in blue.
Figure 2

The single unit tile is circled in red. The middle 4 by 5 rectangle is circled in green. The 3 unit tiles on the bottom right are circled in blue.
Figure 3

The red circles point out the left arms, the green circles point out the rectangles, and the blue circles point out the right arms.

Notice the following:
The length of the rectangle in Figure 1 is units units; the rectangle in Figure 2 is units units; and the rectangle in Figure 3 is units units.

First, look at the left arm. It remains constant in each of these figures, with a value of .

Let Figure number.
There is a rule for the size of the rectangles: , where represents the length and represents the width.

Now, consider the right arms. Its length matches its corresponding figure number.

left arm rectangle right arm

Now simplify.