All the solutions provided in **McGraw Hill My Math Grade 3 Answer Key PDF Chapter 13 Lesson 2 Perimeter **will give you a clear idea of the concepts.

## McGraw-Hill My Math Grade 3 Answer Key Chapter 13 Lesson 2 Perimeter

The distance around the outside of a figure or shape is its perimeter.

**Math in My World**

**Example 1**

Warren and his dad will fence in the backyard for his new puppy. Find the perimeter of the backyard.

To find the perimeter if you already know the side lengths, add the lengths of the sides.

9 + 12 + 9 + 12 = ______________

So, the perimeter is ____________ meters.

Answer:

Given that,

The length of the backyard = 12m

The breath of the backyard = 9m.

The perimeter of the backyard = 9 + 12 + 9 + 12 = 42m

So, the perimeter is 42 meters.

**Example 2**

Find the perimeter of the shaded rectangle.

Count the distance around the figure, or add the lengths of the sides.

4 + 5 + 4 + 5 = ____________

So, the perimeter is ___________ units.

Answer:

Given that,

The length of the shaded rectangle is 5 units.

The breath of the shaded rectangle is 4 units.

The perimeter of the shaded rectangle is 4 + 5 + 4 + 5 = 18.

So, the perimeter is 18 units.

**Example 3**

The perimeter of the figure is 33 feet. Find the unknown side length. Write an equation.

The unknown side length is ____________ feet, since 29 + ___________ = 33.

Answer:

Given that the figure is a pentagon.

The perimeter of the pentagon is 33 feet.

The know lengths of the pentagon are 8, 6, 6, and 9.

Therefore the unknown length is 8 + 6 + 6 + 9 + ? = 33

29 +? = 33

33 – 29 = ?

4 =?

The unknown length of the pentagon is 4 feet.

**Talk Math**

If a triangle had three equal sides and its perimeter was 15 units, how could you find the length of each side?

Answer:

Given that,

The triangle is equilateral.

The perimeter of the triangle is 15 units.

The formula for the perimeter of the triangle is a + b + c.

15 = 5 + 5 + 5.

The length of the each side of the triangle is 5 units.

**Guided Practice**

**Find the perimeter of each figure.**

Question 1.

The perimeter is ___________ centimeters.

Answer:

The perimeter of the given figure is 2 + 5 + 3 + 6 = 16.

The perimeter is 16 centimeters.

Question 2.

The perimeter is ___________ units.

Answer:

Let us assume the units of the figure has show below**
**The perimeter of the given figure is 6 + 6 + 3 + 3 + 3 = 21.

The perimeter is 21 units.

**Independent Practice**

**Find the perimeter of each figure.**

Question 3.

The perimeter is ___________ centimeters.

Answer:

The perimeter of the given figure is 2 + 2 + 2 + 4 = 10.

The perimeter is 10 centimeters.

Question 4.

The perimeter is ___________ units.

Answer:

Let us assume the units of the figure has shown below.

The perimeter of the given figure is 6 + 4 + 2 + 4 + 2 = 18 units.

The perimeter is 18 units.

Question 5.

The perimeter is ___________ centimeters.

Answer:

The perimeter of the given figure is 2 + 2 + 2 + 2 + 2 + 3 = 13.

The perimeter is 13 centimeters.

Question 6.

The perimeter is ___________ feet.

Answer:

The perimeter of the of the given figure is 3 + 2 + 2 + 3 + 1 =11.

The perimeter is 11 feet.

**Algebra Find the unknown side length for each figure. The perimeter of each figure is 50 centimeters.**

Question 7.

The unknown is ___________ centimeters.

Answer:

Given that,

The figure is rectangle.

The the rectangle the opposite sides are equal.

length = 17 cm.

Breath = 8 cm.

The unknown is 8 centimeters.

Question 8.

The unknown is ___________ centimeters.

Answer:

Given that,

The given triangle is isosceles triangle.

In the isosceles triangle two sides are equal.

So, the unknow side length is 12 centimeters.

The unknown is 12 centimeters.

Question 9.

The unknown is ___________ centimeters.

Answer:

Given that,

The figure is pentagon.

In the given pentagon all sides are equal.

The unknown is 10 centimeters.

Question 10.

The unknown is ___________ centimeters.

Answer:

Given that,

The formula for the perimeter of the trapezium is a + b + c + d.

The perimeter of the trapezium is 12 + 16 + 16 + d

= 44 + d

Let us assume d = 8

= 44 + 8

= 54

The unknown is 54 centimeters.

**Problem Solving**

Question 11.

Maya’s family is building a deck. The deck has 6 sides. Each side of the deck is 12 feet long. What is the perimeter of the deck?

Answer:

Given that,

Maya’s family is building a deck.

The deck has 6 sides. It means the desk is in the shape of hexagon.

Each side of the deck is 12 feet long.

The perimeter of the hexagon is 6a.

= 6(12)

= 72 feet.

Therefore the perimeter of the desk is 72 feet.

Question 12.

The figure below has a perimeter of 21 feet. Find the length of the missing side.

Answer:

Given that,

The perimeter of the given figure is 21 feet.

The unknown side length is 3 + 3 + 5 + 6 = 21.

17 = 21

21 – 17 = 4.

Therefore the unknown side length is 4 ft.

Question 13.

**Mathematical PRACTICE** Use Algebra A fountain has three sides. Its perimeter is 36 meters. One side is 12 meters and another is 15 meters. What is the length of the third side?

Answer:

Given that,

The perimeter of the triangle is 36 meters.

One side is 12 meters and another is 15 meters.

The formula for the perimeter of the triangle is a + b + c

= 12 + 15 + c = 36.

27 + c = 36

36 – 27 = c

c = 9

The length of the third side is 9 meters.

**HOT Problems**

Question 14.

**Mathematical PRACTICE** Model Math In the space below, draw and label a figure that has a perimeter of 24 inches.

Answer:

Given that,

The perimeter of the figure is 24 inches.

The perimeter of the rectangle is 8 + 8 + 4 + 4 = 24 inches.

Question 15.

**Building on the Essential Question** What operation can you use to find an unknown side length, if you know the perimeter? Explain.

Answer:

To find the unknow side length if you know the perimeter subtract the unknow sides from the perimeter to find the length of the missing side.

### McGraw Hill My Math Grade 3 Chapter 13 Lesson 2 My Homework Answer Key

**Practice**

**Find the perimeter of each figure.**

Question 1.

The perimeter is ______________ centimeters.

Answer:

The perimeter of the given figure is 4 + 10 + 4 + 10 = 24.

The perimeter is 24 centimeter.

Question 2.

The perimeter is ______________ units.

Answer:

Let us assume the units of the figure as given below.

The perimeter of the figure is 3 + 3 + 3 + 1 + 1 + 3 + 3 + 5 = 22.

**Algebra Find the unknown side length for each figure. The perimeter of each figure is 30 meters.**

Question 3.

The unknown is _____________ meters.

Answer:

Given that,

The figure is rectangle.

In the rectangle the opposite sides are equal.

The opposite side of the unknown value is 5 m.

Therefore the unknown value is 5 meters.

Question 4.

The unknown is _____________ meters.

Answer:

Given that,

The figure is pentagon.

In pentagon all sides are equal.

The known sides of the pentagon is 6m.

Therefore the unknown side length is 6 meters.

**Problem Solving**

Question 5.

**Mathematical PRACTICE** Use Algebra A garden has eight equal sides and has a perimeter of 56 meters. Circle the equation that gives the length, in meters, of each side.

56 + 8 = 65

56 – 8 = 48

56 ÷ 8 = 7

Answer:

Given that,

A garden has 8 equal sides.

The perimeter of the garden is 56 meters.

The circle equation gives the length of each side.

Question 6.

All professional baseball teams’ playing fields are the same size. The three bases and home plate make a diamond that is 90 feet on each side. What is the perimeter of the diamond?

Answer:

Given that,

The diamond is in the shape of rhombus.

The perimeter of the rhombus is 4a = 4(90) = 360 feet.

Therefore the perimeter of the diamond is 360 feet.

**Vocabulary Check**

Question 7.

Describe perimeter in your own words.

Answer:

The perimeter is define has the total length of the boundary.

**Test Practice**

Question 8.

What is the perimeter of the shaded figure?

(A) 18 units

(B) 20 units

(C) 10 units

(D) 9 units

Answer:

The shaded figure is in the shape of square.

In the square all sides are equal.

The perimeter of the shaped figure is 20 = 5 + 5 + 5 + 5.

Option B is the correct answer.