# McGraw Hill Math Grade 3 Chapter 12 Lesson 6 Answer Key Finding a Perimeter or Unknown Side Length

## McGraw-Hill Math Grade 3 Answer Key Chapter 12 Lesson 6 Finding a Perimeter or Unknown Side Length

Solve

Find the perimeter.

Question 1.

16 cm

Question 2.

15 ft

Explanation:
Perimeter of the triangle is sum of all the sides
That is 5 + 5 + 5 = 15
So, perimeter is 15 ft.

Question 3.

4 m

Explanation:
Perimeter of the square is sum of all the sides
That is 1 + 1 + 1 + 1 = 4
So, perimeter is 4 m.

Find the length of the unknown side.

Question 4.

perimeter: 30 m
unknown side: ___________
Unknown side = 10 m.

Explanation:
Given Perimeter = 30 m
Perimeter of the triangle is sum of all the sides
That is 10 + 10 + ? = 30
20 + ? = 30
30 – 20 = 10
So, unknown side = 10 m.

Question 5.

perimeter: 14 in
unknown side: _____________
Unknown side = 4 in

Explanation:
Given perimeter = 14 in
Perimeter of a shape is sum of all the sides
2 + 3 + 2 + 3Â  + ? = 14
10 + ? = 14
14 – 10 = 4
So, unknown side = 4 in.

Question 6.

perimeter: 16 ft
unknown side: _____________