All the solutions provided in McGraw Hill My Math Grade 3 Answer Key PDF Chapter 13 Lesson 3 Understand Area will give you a clear idea of the concepts.
McGraw-Hill My Math Grade 3 Answer Key Chapter 13 Lesson 3 Understand Area
A square with a side length of one unit is called a unit square.
A unit square has one square unit of area and can be used to measure area. Area is the number of square units needed to cover a figure without overlapping.
Draw It
Draw and shade two different rectangles that each have an area of 20 square units.
Use the 10-by-10 grid.
To shade a rectangle with 20 square units, you need to shade a rectangle made up of 20 unit squares.
1. Shade 20 unit squares so that they form a rectangle.
What is the perimeter of your rectangle?
2. Shade another 20 unit squares so that they form a different rectangle.
What is the perimeter of your rectangle?
Answer:
Draw the rectangle with 20 units squares and shade the rectangle.
The formula for the perimeter of the rectangle is 2(l + b)
l = 2 unit squares.
b = 10 unit squares.
= 2(2 + 10) = 24 unit squares.
Therefore the perimeter of the shaded rectangle is 24 unit squares.
The another rectangle is
l = 10 unit squares.
b = 2 unit squares.
= 2(2 + 10) = 24 unit squares.
Therefore the perimeter of the another shaded rectangle is 24 unit squares.
Both the rectangles have same perimeter.
You can also think of area as the amount of space enclosed by a figure.
Try It
Use a rubber band and a geoboard to make the rectangle shown. What is the area of the rectangle in square units?
How many unit squares are enclosed by the rubber band? ___________
So, the area is ____________ square units.
Answer:
Given that,
The shape is in the form of rectangle.
There are 3 unit squares are enclosed by the rubber band.
The formula for the area of the rectangle is l x b.
Here
length = 3.
Breath = 1.
Therefore the are of the rectangle is 3 square units.
So, the area is 3 square units.
Try It
What is the area of the figure at the right?
The figure has no gaps or overlaps. So, count the shaded unit squares.
How many unit squares are enclosed, or covered, by the figure? ___________
So, the area is ___________ square units.
Answer:
We know that if the unit square has one square unit of area and it can be used to measure the area.
The number of unit squares in the figure is 24 unit squares.
Therefore there are 24 unit squares are enclosed, or covered, by the figure.
So, the area is 24 square units.
Talk About It
Question 1.
Mathematical PRACTICE Be Precise Without drawing, tell how many different rectangles have an area of 5 square units. Explain.
Answer:
We have only one rectangle with an area of 5 square units. Because 5 is an a prime number. So the width of 1 unit and length of 5 units.
Question 2.
How can the term unit square help you to remember that area is measured in square units?
Answer:
The term unit square is useful to find the area is measured in square units. Because the number of unit squares is equal to the area measured in the square units.
Practice
Count unit squares to find the area of each figure.
Question 3.
Area: ______________
Answer:
Given that,
The figure has 20 unit squares.
The number of unit squares is equal to the area measured in the square units.
Therefore the area of the given figure is 20 square units.
Question 4.
Area: ______________
Answer:
Given that,
The figure has 18 unit squares.
The number of unit squares is equal to the area measured in the square units.
Therefore the area of the given figure is 18 square units.
Question 5.
Draw and shade a rectangle with an area of 36 square units.
What is the perimeter of the figure you drew?
_____________ units
Answer:
Given that,
Draw a rectangle with an area of 36 square units.
The number of unit squares is equal to the area measured in the square units.
Now draw a rectangle with 4 x 9 unit squares and shade it.
The formula for the perimeter of the rectangle is 2(l + b)
length = l = 4.
Breath = b = 9
= 2(9 + 4) = 2(13) = 26.
Therefore the perimeter of the rectangle is 26 square units.
Question 6.
Draw and shade a different rectangle with an area of 36 square units.
What is the perimeter of the figure you drew?
_____________ units
Answer:
Given that,
Draw a rectangle with an area of 36 square units.
The number of unit squares is equal to the area measured in the square units.
Now draw a rectangle with 9 x 4 unit squares and shade it.
The formula for the perimeter of the rectangle is 2(l + b)
length = l = 4.
Breath = b = 9
= 2(9 + 4) = 2(13) = 26.
Therefore the perimeter of the rectangle is 26 square units.
Question 7.
A figure without gaps or overlaps can be covered by 14 unit squares. Circle the correct area of the figure.
4 square units
7 square units
14 square units
Answer:
We know that,
The number of unit squares is equal to the area measured in the square units.
The area of the figure is 14 square units.
Apply It
Question 8.
Jared used a rubber band and geoboard to create the rectangle at the right. What is the area of the rectangle?
Answer:
Given that,
The shape is rectangle.
The rectangle has 12 unit squares.
The number of unit squares is equal to the area measured in the square units.
So, the area of the rectangle is 12 square units.
Question 9.
Mathematical PRACTICE Make a Plan Morgan will help her parents tile a new bathroom floor. She drew a sketch of the bathroom floor. Each square unit represents one tile. How many tiles are needed to tile the floor?
Answer:
Given that,
She drew a sketch of the bathroom floor.
Each square unit represents one tile.
Therefore the number of tiles needed are 10 x 7 = 70.
Question 10.
Mathematical PRACTICE Model Math Draw and shade a figure (not a rectangle) with an area of 21 square units. The figure should not have any gaps or overlaps.
Answer:
Given that,
Draw a figure with an area of 36 square units.
The number of unit squares is equal to the area measured in the square units.
Now draw a figure with 21 unit squares and shade it.
Therefore the area of the figure is 21 square units.
Question 11.
Find the perimeter of the figure you drew in Exercise 10.
Answer:
The perimeter of the above figure is 5 + 5 + 4 + 4 + 1 + 1 = 20 units.
Therefore the perimeter of the above figure is 20 units.
Write About It
Question 12.
Describe one way that area can be measured.
Answer:
The one way that area can be measured by comparing the shape to squares of the fixed size.
McGraw Hill My Math Grade 3 Chapter 13 Lesson 3 My Homework Answer Key
Practice
Count unit squares to find the area of each figure.
Question 1.
Area: ______________
Answer:
Given that,
The figure has 21 unit squares.
The number of unit squares is equal to the area measured in the square units.
Therefore the area of the given figure is 21 square units.
Question 2.
Area: ______________
Answer:
Given that,
The figure has 24 unit squares.
The number of unit squares is equal to the area measured in the square units.
Therefore the area of the given figure is 24 square units.
Question 3.
A shape is covered by 40 unit squares. What is the area of the shape?
Answer:
The number of unit squares is equal to the area measured in the square units.
Therefore the area of the covered shape is 40 square units.
Question 4.
Draw and shade a rectangle with an area of 30 square units.
Answer:
Given that,
Draw a rectangle with an area of 30 square units.
The number of unit squares is equal to the area measured in the square units.
Now draw a rectangle with 10 x 3 unit squares and shade it.
Therefore the area of the rectangle is 30 square units.
Question 5.
Draw and shade a different rectangle with an area of 30 square units.
Answer:
Given that,
Draw a rectangle with an area of 30 square units.
The number of unit squares is equal to the area measured in the square units.
Now draw a rectangle with 3 x 10 unit squares and shade it.
Therefore the area of the rectangle is 30 square units.
Problem Solving
Question 6.
Caitlyn used a rubber band and geoboard to make the rectangle shown. What is the area of the rectangle?
Answer:
Given that,
The shape is rectangle.
The rectangle has 4 unit squares.
The number of unit squares is equal to the area measured in the square units.
So, the area of the rectangle is 4 square units.
Question 7.
Mathematical PRACTICE Plan Your Solution A figure can be covered by 28 unit squares, without any gaps or overlaps. What is the area of the figure?
Answer:
We know that,
The number of unit squares is equal to the area measured in the square units.
The unit squares is 28.
Therefore the area of the figure is 28 square units.
Vocabulary Check
Choose the correct word(s) to complete each sentence.
area
square units
unit square
Question 8.
______________ is measured in _____________ and represents the number of those needed to cover a figure without overlapping.
Answer:
Area is measured in unit square and represents the number of those needed to cover a figure without overlapping.
Question 9.
A square with a side length of one unit is called a _______________.
Answer:
A square with a side length of one unit is called a unit square.