CPM Homework Help : ACC6 Problem 3-20

Study the dot pattern below.

$\Large\begin{array}{c c} \bullet & \bullet\\ \bullet & \bullet \end{array}\\ \, \text{Fig. 1}$

$\Large\begin{array}{c c} \bullet & \bullet\\ \bullet & \bullet\\ \bullet & \bullet \end{array}\\ \, \text{Fig. 2}$

$\text{Fig. 3}$

$\Large\begin{array}{c c} \bullet & \bullet\\ \bullet & \bullet\\ \bullet & \bullet\\ \bullet & \bullet\\ \bullet & \bullet \end{array}\\ \, \text{Fig. 4}$

$\text{Fig. 5}$

Draw the $3$ ^rd and $5$ ^th figures.
Hint (a):
Can you see a pattern in the completed figures? Use this pattern to complete figures 3 and 5.
How many dots will there be in the $50$ ^th figure?
Hint (b):
The number of dots can be found by multiplying the figure number by $2$ and then adding $2$ . Do this with the figure number equal to $50$ .
Answer (b):
$102$ dots
Is there a figure that will have exactly $38$ dots? If so, which figure is it?

Hint (c):
Do the same process as above, but in reverse. Subtract $2$ and then divide by $2$ . If you get a whole number, that is the figure number.

Use the eTool below to create the patterns for Fig. 3 and Fig. 5.
Click the link at right for the full version of the eTool: