Math 6 Plus Unit 8 Introducing Proportional Relationships Family Materials
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Course
MISC
Subject
Mathematics
Date
Jan 9, 2024
Type
Pages
6
Uploaded by MinisterKnowledgeDragon70
Math
6 Plus
Unit
8
: Introducing Proportional Relationships
Homework Resources (For Families)
Representing Proportional Relationships with Tables
This week your student will learn about proportional relationships. This builds on the work they did with equivalent
ratios in grade 6. For example, a recipe says “for every 5 cups of grape juice, mix in 2 cups of peach juice.” We
can make different-sized batches of this recipe that will taste the same.
The amounts of grape juice and peach juice in each of these batches form equivalent ratios.
The relationship between the quantities of grape juice and peach juice is a
proportional relationship
. In a table
of a proportional relationship, there is always some number that you can multiply by the number in the first column
to get the number in the second column for any row. This number is called the
constant of proportionality.
In the fruit juice example, the constant of proportionality is 0.4. There are 0.4 cups of peach juice per cup of grape
juice.
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Here is a task you can try with your student:
Using the recipe “for every 5 cups of grape juice, mix in 2 cups of peach juice”
1.
How much peach juice would you mix with 20 cups of grape juice?
2.
How much grape juice would you mix with 20 cups of peach juice?
Solution:
1.
8 cups of peach juice. Sample reasoning: We can multiply any amount of grape juice by 0.4 to find the
corresponding amount of peach juice, 20
⋅
(0.4)=8.
2.
50 cups of grape juice. Sample reasoning: We can
divide
any amount of peach juice by 0.4 to find the
corresponding amount of grape juice, 20÷0.4=50.
Representing Proportional Relationships with Equations
This week your student will learn to write equations that represent proportional relationships. For example, if each
square foot of carpet costs $1.50, then the cost of the carpet is proportional to the number of square feet.
The
constant of proportionality
in this situation is 1.5. We can multiply by the constant of proportionality to find the
cost of a specific number of square feet of carpet.
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We can represent this relationship with the equation c=1.5f, where f represents the number of square feet, and c
represents the cost in dollars. Remember that the cost of carpeting is always the number of square feet of
carpeting times 1.5 dollars per square foot. This equation is just stating that relationship with symbols.
The equation for any proportional relationship looks like y=kx, where x and y represent the related quantities and
k is the constant of proportionality. Some other examples are y=4x and d=13
t
. Examples of equations that do not
represent proportional relationships are y=4+x, A=6s
2
, and w=36L.
Here is a task to try with your student:
1.
Write an equation that represents that relationship between the amounts of grape juice and peach juice
in the recipe “for every 5 cups of grape juice, mix in 2 cups of peach juice.”
2.
Select
all
the equations that could represent a proportional relationship:
A. K=C+273
B. s=14p
C. V=s
3
D.
h=14−x
E. c=6.28r
Solution:
1.
Answers vary. Sample response: If p represents the number of cups of peach juice and g represents
the number of cups of grape juice, the relationship could be written as p=0.4g. Some other equivalent
equations are p=25g, g=52p, or g=2.5p.
2.
B and E. For the equation s=14p, the constant of proportionality is 14. For the equation c=6.28r, the
constant of proportionality is 6.28.
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