All the solutions provided in **McGraw Hill My Math Grade 3 Answer Key PDF Chapter 13 Lesson 1 Find Perimeter **will give you a clear idea of the concepts.

## McGraw-Hill My Math Grade 3 Answer Key Chapter 13 Lesson 1 Find Perimeter

Perimeter is the distance around the outside of a figure, or shape. You can estimate and measure perimeter.

**Measure It**

1. Estimate the perimeter, in centimeters, of a piece of notebook paper. Record the results in the table below.

2. Use a centimeter ruler to find the perimeter to the nearest centimeter. Find the length of each side. Then add the side lengths. Record the results in the table.

3. Repeat Steps 1 and 2 for each object listed in the table.

Answer:

Here the piece of notebook paper, math book, desktop, and chalkboard or whiteboard is in the shape of rectangle.

The formula for the perimeter of the rectangle is P = 2(l + w).

The estimate perimeter of the piece of notebook paper is 18cm.

Assume that the length of the piece of notebook paper is 6cm.

Width of the piece of notebook paper is 4cm.

The Actual perimeter of the piece of notebook paper is 2(6 + 4) = 2(10) = 20cm.

The estimate perimeter of math book is 23cm.

Assume that the length of the Math book is 7cm.

Width of the math book is 6cm.

The Actual perimeter of the math book is 2(7 + 6) = 2(13) = 26cm.

The estimate perimeter of the desktop is 124cm.

Assume that the length of the desktop is 40cm.

Width of the desktop is 25cm.

The Actual perimeter of the desktop is 2(40 + 25) = 2(65) = 130cm.

The estimate perimeter of the chalkboard or whiteboard is 200cm.

Assume that the length of the chalkboard or whiteboard is 59cm.

Width of the chalkboard or whiteboard is 44cm.

The Actual perimeter of the chalkboard or whiteboard is 2(59 + 44) = 2(103) = 206cm.

An inch is larger than a centimeter. One inch is about halfway between 2 and 3 centimeters.

**Try It**

Using the same objects from the first activity, estimate and measure each perimeter to the nearest inch.

1. Estimate the perimeter, in inches, of a piece of notebook paper. Record the results in the table below.

2. Use an inch ruler to find the perimeter to the nearest inch. Record the results in the table.

3. Repeat Steps 1 and 2 for each object listed in the table.

Answer:

From the above question we know that,

The estimate perimeter of the piece of notebook paper is 18cm.

18cm = 7.086 inches.

The Actual perimeter of the piece of notebook paper is 2(6 + 4) = 2(10) = 20cm.

20cm = 7.874

The estimate perimeter of math book is 23cm.

23cm = 9.055inches.

The Actual perimeter of the math book is 2(7 + 6) = 2(13) = 26cm.

26cm = 10.236 inches.

The estimate perimeter of the desktop is 124cm.

124cm = 48.819inches.

The Actual perimeter of the desktop is 2(40 + 25) = 2(65) = 130cm.

130cm = 51.181 inches.

The estimate perimeter of the chalkboard or whiteboard is 200cm.

200cm = 78.740 inches

The Actual perimeter of the chalkboard or whiteboard is 2(59 + 44) = 2(103) = 206cm.

206 cm = 81.102 inches.

**Talk About It**

Question 1.

**Mathematical PRACTICE** Explain to a Friend Why is it important to estimate the perimeter before finding its exact measurement?

Answer:

It is important because it can help you to get an idea about the real answer.

For example you have a real answer is 29.

The estimation answer is 30.

Question 2.

Compare the perimeters of the objects in centimeters to the perimeters in inches. What do you notice?

Answer:

Comparing the perimeters of the objects in centimeters and inches you can find the difference in perimeter.

1 inch = 2.54 cm.

Question 3.

After measuring the length of each side of an object, what operation did you use to find the perimeter? Explain.

Answer:

After measuring the length of each side of an abject you need to do the addition operation to find the perimeter.

**Practice It**

**Estimate the perimeter of each figure in centimeters. Then measure the perimeter to the nearest centimeter.**

Question 4.

Estimate: ______________

Actual: ______________

Answer:

Given that,

The figure is rectangle.

The estimate perimeter of the rectangle is 20.

Assume that the length of the rectangle is 5cm.

The width of the rectangle is 4cm.

The formula for the perimeter of the rectangle is P = 2(l + w)

= 2(5 + 4) = 2(9) = 18.

The perimeter of the rectangle is 18 cm.

The 18cm rounded to the nearest centimeter is 20 cm.

Question 5.

Estimate: ______________

Actual: ______________

Answer:

Given that,

The figure is triangle.

The estimate perimeter of the triangle is 10cm.

Assume that the side length of the triangle is 3 inches.

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

= 3 + 3 + 3 = 9

The perimeter of the triangle is 9 cm.

The 9cm rounded to the nearest centimeter is 10 cm.

**Estimate the perimeter of each figure in inches. Then use an inch ruler to measure the perimeter to the nearest inch.**

Question 6.

Estimate: ______________

Actual: ______________

Answer:

The estimate perimeter of the pentagon is 8.

The formula for the perimeter of the pentagon is 5a.

The side length of the pentagon is 2 inches.

The perimeter of the pentagon is 5(2) = 10 inches.

10 inches rounded to the nearest inch is 10 inches.

Question 7.

Estimate: ______________

Actual: ______________

Answer:

Given that,

The figure is trapezium.

The estimate perimeter of the trapezium is 26 inches.

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

length of a side = 4.

length of b side = 7.

length of c side = 6

length of d side = 7.

The perimeter of the trapezium is 4 + 7 + 6 + 7 = 24 inches.

The 24 inches rounded to the nearest inch is 20 inches.

Question 8.

Circle whether the number of inches used to measure the perimeter of a figure would be larger or smaller than the number of centimeters.

larger

smaller

Answer:

The inches used to measure the object is larger than the centimeters.

**Apply It**

Question 9.

**Mathematical PRACTICE** Use Number Sense Rebecca used a centimeter ruler to measure the perimeter of the figure below. Which estimate is closest to the actual perimeter, 6 centimeters or 12 centimeters?

Answer:

Given that,

The figure is hexagon.

The formula for the perimeter of the hexagon is 6a.

The estimation of the actual perimeter is closer to the 6 centimeters.

Question 10.

Antoine built a picture frame out of wood. He used an inch ruler to measure the perimeter of the frame. If the lengths of the sides of the frame are 8 inches, 6 inches, 8 inches, and 6 inches, what is the perimeter of the frame?

Answer:

Given that,

Antoine built a picture frame out of wood.

The lengths of the sides of the frame are 8 inches, 6 inches, 8 inches, and 6 inches.

The shape of the frame is in rectangle.

The length = 8 inches.

The width = 6 inches.

The formula for the perimeter of the rectangle is 2(l + w) = 2(8 + 6) = 2(14) = 28.

Therefore the perimeter of the frame is 28 inches.

Question 11.

**Mathematical PRACTICE** Justify Conclusions The perimeter of an object is 10 inches. Will the perimeter of the object to the nearest centimeter be less than, greater than, or equal to 10? Explain.

Answer:

Given that,

The perimeter of an object is 10 inches.

The 10 inches = 25.4 cm.

25.4 cm nearest to the centimeter is 26.

The perimeter of the object to the nearest centimeter is greater than 10.

**Write About It**

Question 12.

How is perimeter related to the operation of addition?

Answer:

The perimeter is the outside length of an object.

To find the perimeter you need to know the 1 or 2 sides length.

The perimeter is the adding of lengths of an object.

### McGraw Hill My Math Grade 3 Chapter 13 Lesson 1 My Homework Answer Key

**Practice**

**Estimate the perimeter of each figure in centimeters. Then measure the perimeter to the nearest centimeter.**

Question 1.

Estimate: ______________

Actual: ______________

Answer:

Given that,

The figure is a rectangle.

The estimate perimeter of the rectangle is 13 cm

The formula for the perimeter of the square is 2(l + w).

Assume that the length of the rectangle is 2 cm

The width of the rectangle is 6 cm.

The actual perimeter of the square is 2(2 + 6) = 2(8) = 16 cm.

The 16cm rounded to the nearest centimeter is 20 cm.

Question 2.

Estimate: ______________

Actual: ______________

Answer:

Given that,

The figure is a pentagon.

The estimate perimeter of the pentagon is 14. cm.

The formula for the perimeter of the pentagon is 5a.

Assume that the side length of the pentagon is 3 cm.

The actual perimeter of the pentagon is 5(3) = 15 cm.

The 15cm rounded to the nearest centimeter is 20 cm.

**Estimate the perimeter of each figure in inches. Then use an inch ruler to measure the perimeter to the nearest inch.**

Question 3.

Estimate: ______________

Actual: ______________

Answer:

Given that,

The figure is a triangle.

The estimate perimeter of the triangle is 8 inches.

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

Assume that the side length of triangle a = 2inches, b = 2 inches and c = 2 inches.

The actual perimeter of the triangle is a + b + c = 2 + 2 + 2 = 6 inches.

The 6 inches rounded to the nearest inch is 10 inches.

Question 4.

Estimate: ______________

Actual: ______________

Answer:

Given that,

The figure is a square.

The estimate perimeter of the square is 7 inches.

The formula for the perimeter of the square is 4a.

Assume that the side length is 2 inches.

The actual perimeter of the square is 4(2) = 8 inches.

The 8 inches rounded to the nearest inch is 10 inches.

**Problem Solving**

Question 5.

**Mathematical PRACTICE** Make Sense of Problems Gina used a centimeter ruler to measure the perimeter of the figure at the right. Which estimate is closest to the actual perimeter, 8 centimeters or 16 centimeters?

Answer:

Given that,

The figure is octagon.

The formula for the perimeter of the octagon is 8a.

The 8 centimeters is closer to the actual perimeter.

Question 6.

**Mathematical PRACTICE** Be Precise Allison used an inch ruler to measure the perimeter of the figure above. Circle the measure that represents the best estimate of the perimeter to the nearest inch.

2 inches

8 inches

12 inches

16 inches

Answer:

The formula for the perimeter of the octagon is 8a.

The 8 centimeters is closer to the actual perimeter.

**Vocabulary Check**

Question 7.

Complete the sentence below with the correct vocabulary word.

perimeter

array

______________ is the distance around a figure, or shape.

Answer:

Perimeter is the distance around a figure or shape.