Hello!
So, we use this formula when finding the area of a rectangle:
A = l × w
The formula for perimeter:
P = 2l + 2w
We have the width but we still need the length to find the perimeter. You see, we multiplied the length by the width to get the AREA, but because we want to find the opposite now, we must use the opposite operation as well.
What's the opposite of multiplication?
Division!
Formula for length:
L = A ÷ w
Substitute:
L = 20 ÷ 5
L = 4 meters
Now that we know what the length and the width of the dog pen is, finding the perimeter will be a piece of cake!
Formula:
P = 2l + 2w
Substitute:
P = 2(4) + 2(4)
P = 16 meters
A N S W E R:
The perimeter of the dog pen is 16 meters.