We included HMH Into Math Grade 3 Answer Key PDF Module 11 Lesson 3 Find Unknown Side Lengths to make students experts in learning maths.
HMH Into Math Grade 3 Module 11 Lesson 3 Answer Key Find Unknown Side Lengths
I Can find the unknown side length of a polygon when I know the other side lengths and the perimeter of a polygon. I can add, subtract, multiply, and divide to find the unknown side length.
Spark Your Learning
Pablo has a length of wood that measures 24 feet. He wants to use the total length to build a border around a flower bed in his yard.
How can you show three different rectangles that have a perimeter of 24 units?
Answer:
Turn and Talk What strategies did you use to draw the rectangles?
Answer:
p = 24
24 = 2 (l + w)
l + w = 12
let us consider l = 6
and w = 6
6 + 6 = 12
and
let us consider l = 4
and w = 8
8 + 4 = 12
and
let us consider l = 5
and w = 7
7 + 5 = 12
Build Understanding
Question 1.
Kai draws this rectangle.
A. What do you know about the side lengths and perimeter of a rectangle?
Answer:
p = 2(l + w)
18 = 2l + 12
2l = 18 – 12
2l = 6
l = 3
length is 3 inches
B. How can you use what you know about the perimeter of the rectangle to write an equation to find the unknown side length, s?
Answer:
p = 2(l + w)
18 = 2l + 12
2l = 18 – 12
2l = 6
l = 3
length is 3 inches
Step It Out
Question 2.
Kimi’s sister has a play yard in the shape of a hexagon. How can you find the unknown side length?
A. Hexagons have _______ sides. This hexagon appears to have sides that are all the same length.
Answer:
Hexagons have 6 sides. This hexagon appears to have sides that are all the same length.
B. Use the perimeter to write an addition equation to find the side lengths. Use the letter s to stand for the unknown side lengths.
Answer:
perimeter = sum of all sides
p = 6s
let s be the length of one side.
C. What multiplication equation can you write to find the side lengths?_______ × s = 54
Answer:
6 x s = 54
s = 9
D. Write a related division equation.
Answer:
54 ÷ 6 = 9
9 x 6 = 54
E. Solve to find the unknown length, s = ____________
Answer:
area = 6s
6s = 54
s = 9
Turn and Talk How could you find an unknown side length of a polygon when given the perimeter and all but one side length?
Answer:
p = sum of all sides
or
we can use p = 2(l + w)
by this we find the unknown length.
Question 3.
The perimeter of this polygon is 26 centimeters. How can you find the unknown side length?
A. Write an equation to find the perimeter. Use the letter n to stand for the unknown side length.
Answer:
p = 26 centimeters
p = 9 + 6 + 3 + n
26 = 18 + n
n = 26 – 18
n = 8
B. Add the lengths of the sides you know.
Answer:
p = 9 + 6 + 3 + 8
26 = 26
C. Rewrite your original addition equation using the sum you found.
Answer:
p = sum of all sides
p = 9 + 6 + 3 + 8
26 = 26
D. Write a related subtraction equation.
Answer:
n = 26 – 18
E. Solve to find the unknown side length.
n = ___________
Answer:
p = 26 centimeters
p = 9 + 6 + 3 + n
26 = 18 + n
n = 26 – 18
n = 8
Check Understanding
Question 1.
The perimeter of this polygon is 41 centimeters. What is the unknown side length?
c = __________
Answer:
c = 7cm
Explanation:
p = sum of all sides
41 = 12 + 10 + 8 + 4 + c
41 = 34 + c
c = 41 – 34
c = 7
Question 2.
The perimeter of a square is 32 inches. What is the length of side s?
Answer:
the length of side s = 8
Explanation:
The perimeter of a square is 32 inches
The perimeter of a square = 4 x s
4s= 32
s = 32 ÷ 4
s = 8
On Your Own
Question 3.
Attend to Precision lima has this rectangular blanket. The perimeter is 24 feet. What is the unknown side length?
l = ____________
Answer:
8 feet is the unknown side length
Explanation:
The perimeter is 24 feet.
p = 2 (l + w)
24 = 2(l + 4)
24 = 2l + 8
2l = 16
l = 16 ÷ 2
l = 8
Find the unknown side lengths.
Question 4.
Perimeter = 25 centimeters
b = ___________
Answer:
b = 6 cm
Explanation:
perimeter = sum of all sides
p = 8 + 4 + 7 + b
25 = 19 + b
b = 25 – 9
b = 6
Question 5.
Perimeter = 30 yards
s = ___________
Answer:
length of one side = 5
perimeter = 6s
6s = 30
s = 30 ÷ 6
s = 5
Question 6.
Critique Reasoning Karley says that the unknown side lengths of this hexagon are 3 meters. Is Karley correct? Use equations to help you explain.
Answer:
no, he is not correct
the length of unknown sides are 9meters
perimeter = sum of all sides
30 = 3 + 3 + 3 + 3 + w + w
30 = 12 + 2w
2w = 30 – 12
2w = 18
w = 18 ÷ 2
w = 9
I’m in a Learning Mindset!
What strategies did I use to find the perimeter of polygons with an unknown side length?
Answer:
1) perimeter = sum of all sides
2) perimeter = 2 (l + w)