One Way
Lesson
11-3A
Area of a Rectangle
How can you find the
area of a rectangle?
Common
Core
5.NF.4.b Find the area of
a rectangle with fractional
side lengths by tiling it
with unit squares of the
appropriate unit fraction
side lengths, and show
that the area is the same
as would be found by
multiplying the side
lengths. Multiply fractional
side lengths to find areas of
rectangles, and represent
fraction products as
rectangular areas. Also
5.NF.4
Draw Jenny’s garden
on a 12 3 12 grid.
__
​ 3 ​5 ___
​  9  ​ 
Jenny’s garden is a rectangle that
is __
​ 34 ​yard long and __
​ 23 ​yard wide.
What is the area of her garden?
4 12
8
__
​ 23 ​5 ___
​ 12
  ​ 
39
4 12
28
3 12
Jenny’s garden is
The area of a figure is the
amount of surface it covers.
___
​  72  ​ 5 __
​ 1 ​square yard.
144
2
MATHEMATICAL
Guided Practice
PRACTICES
Do you know HOW?
Do you UNDERSTAND?
1. Find the area of a rectangle with sides
of lengths __
​ 23 ​foot and __
​ 12 ​foot.
3. Generalize If you do not remember
the formula for finding the area of a
rectangle, how can you find its area?
2. Find the area of a square with sides of
length __
​ 34 ​inch.
4. Use Tools Use a 6 3 6 grid to show the
​ 13 ​as the area of a rectangle.
product __
​ 12 ​3 __
Independent Practice
Leveled Practice In 5–8, copy and complete the drawing to find the area of each rectangle.
5. 4 yd
6
1 yd
3
7.
1u
3u
5
6.
1u
1u
4
2u
5
8.
3 cm
10
1u
2
4 cm
5
9. Find the area of a rectangle with side
lengths __
​ 18 ​foot and __
​ 12 ​foot.
38
10. Find the area of a square with side
length __
​ 38 ​inch.
Another Way
Another Way
Draw Jenny’s garden as part of a
square yard. Each small rectangle
1   ​of a square yard.
represents ___
​ 12
Multiply to find the area of the garden.
A5l3w
6
Jenny’s garden is ___
​ 12
   ​5 __
​ 12 ​square
yard.
l is the length and w is the width.
1 yd
3 yd
4
1 yd
6
​ 34 ​3 __
​ 23 ​5 ___
​ 12
  ​ 5 __
​ 12 ​
A 5 __
1 ​square yard.
The area of Jenny’s garden is ​ __
2
2 yd
3
In 11–14, find the area of each rectangle. Give your answer in simplest form.
1"
4
11.
3"
4
12.
3"
4
3"
4
13. Find the area of a square with side
length __
​ 16 ​foot.
14. Find the area of a rectangle with side
1 ​foot and 2 feet.
lengths ​ __
3
MATHEMATICAL
Problem Solving
PRACTICES
15. Use Tools Yuka is placing blue and white tile in her bathroom.
She made a diagram of the layout showing the area of both colors.
Which describes the area of the blue tile?
A
__
​ 2 ​3 __
​ 2 ​
3
3
4 ​3 __
B​ __
​ 4 ​
6 6
C Both A and B
D none of these
16. Construct Arguments Daniel and Paul are working on a multiplication
3
3
 ​in. 5 ___
​ 32
  ​ sq. in. Paul claims that the
problem. Daniel claims that __
​ 14 ​in. 3 ​ __
8
3
   ​sq. in. Who is correct? Explain your answer.
correct answer is ​ ___
12
17. Reasonableness Emilio needs to know how much area to clear to place his
son’s square sandbox. Each side of the sandbox is __
​ 34 ​yard. Find the area that
the sandbox will cover.
18. Persevere Margaret purchased a door mat measuring __
​ 12 ​yard by __
​ 23 ​yard
1 ​square yard, will the mat fit?
for her back door step. If the step measures ​ __
4
Explain.
Lesson 11-3A
39