7th Grade Math

Perimeter is measured in

linear units, such as

inches, feet, centimeters,

and meters.

Sometimes you will know the perimeter of a figure and will want to

determine the length of a side.

Find a Missing Side

The perimeter of the figure at the right is

7 ft

4.7 ft

? ft 4.5 ft

19.7 feet. Find the missing measure.

Step 1 Add the given side lengths.

4.7 + 4.5 + 7 = 16.2

Step 2 Subtract the sum from the perimeter.

19.7 - 16.2 = 3.5

Check 4.7 + 4.5 + 7 + 3.5 = 16.2 

So, the missing measure is 3.5 feet.

Find the missing measure in each figure.

c. P = 20 cm d. P = 14 in.

? cm

8 cm 8 cm

2 in.

4 in.

2 in.

? in.

2 in.

Find the perimeter of each figure.

1.

5 yd

5 yd

4yd 4yd

2. (^) 4.5 cm
   4.5 cm
   1.9 cm 1.9 cm


3. 
   

   12 m
   4.5 m
   13 m

   
   


4. 
   

   3 ft
   6 ft
   7 ft
   10 ft
   Lesson 5 Perimeter 17
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