a For the second figure, it is helpful to think about pushing the inside-sides of the small squares to the outside.
B
b The perimeter increases by 4 between any two consecutive figures.
A
aPerimeter: 4, 8, 12, 16, 20 Pattern: See solution.
B
b 80 units
Practice makes perfect
a The perimeter of a figure measures the sum of the figure's sides. For the first figure, the perimeter is 4 units.
For the second figure, it is helpful to think about pushing the inside-sides of the small squares to the outside, as shown below. Then we can see that the figure has the same perimeter as that of a square with sides measuring 2 units.
We can do the same thing with Figures 3, 4, and 5.
Therefore, the perimeter of each figure is the figure number multiplied by the square's number of sides.
n
4n
=
1
4( 1)
4
2
4( 2)
8
3
4( 3)
12
4
4( 4)
16
5
4( 5)
20
The perimeter increases by 4 units between any two consecutive figures.
b From the Part A, we know that the perimeter P increases by 4 when you go from one figure to the next.
P=4n
By substituting n=20, we can find the perimeter of the 20th figure.
