So first we'll find the perimeter, and to do that we need to find the missing sides. To find the side between the 31 cm line and the 9 cm line, you have to understand that if you added the missing line to the 18 cm line you would get 30 cm, because you can tell just by looking at the picture that they would be the same length as the width of the shape (the 30 cm line).
So to figure out the first missing line you just have to take the 30 cm and subtract the 18 cm.
30 cm - 18 cm = 12 cm
So the missing line at the top equals 12 cm.
To get the other missing line, you go through the same process. You look at the picture and realize that if you added the missing line and the 9 cm line, it would be the same length as the 31 cm line or the length of the shape.
So you would go:
31 cm - 9 cm = 22 cm
If you want to check your answers, you flip the equations a little.
18 cm + 12 cm = ?
18 cm + 12 cm = 30 cm
Does 30 cm = 30 cm?
Yes ^-^
22 cm + 9 cm = ?
22 cm + 9 cm = 31 cm
Does 31 cm = 31 cm?
Yep!
To finish calculating the perimeter, you add all of the sides together.
30 cm + 22 cm + 18 cm + 9 cm + 12 cm + 31 cm = 122 cm
So the perimeter = 122 cm
To find the area of the shape you just have to multiply the length and width of the shape, which in this case would be 31 cm × 30 cm
31 cm × 30 cm = 930 cm2 (it's supposed to be cm squared)
