Finding the Unknown Perimeter

Sally is putting frosting around the edges of the

roof of a gingerbread house. What is the perimeter

of the roof?

• 18 cm

• 16 cm

• 8 cm

• 20 cm

Kyle is adding a border to his triangular flag.

What is the perimeter of the flag?

• 2 inches

• 6 inches

• 3 inches

• 1 inch

Pete glues a rope around his rectangular rodeo sign. His sign has side lengths of 2 feet and 3 feet. The rope costs $4 for each foot. How much does Pete pay for rope?

• $24

• $20

• $10

• $40

Austin’s class is making a poster for

Earth Day. What is the perimeter of

the poster?

• 24 feet

• 21 feet

• 15 feet

• 30 feet

Iris sews a border around a blanket. The blanket has side lengths that are 4 feet and 6 feet. The border material costs $2 for each foot. How much does Iris pay for the border?

• $20

• $12

• $40

• $16

What is the perimeter?

• 40 cm

• 26 cm

• 16cm

Find the unknown side length if the perimeter is 89 inches. Write out your formula to help.

• 15 in.

• 17 in.

• 20 in.

• 13 in.

When finding perimeter you will

• Multiply the numbers

• Add the numbers

If you are finding the PERIMETER what would you do?

• count inside the squares

• count outside the squares on the lines

What is the perimeter of the shape?

• 20 units

• 18 units

• 25 units

• 16 units