Download Direct variation

Direct
variation
Y = mX
Write a direct
variation equation.
Identify the constant
of variation and
interpret its
meaning.
Y
Cost ($)
The cost of private
gymnastic lessons (y)
varies directly with
the number of
sessions (x) as shown
in the graph.
Constant of variation
(slope)
40
35
30
25
20
15
10
5
0
1
10
1
2 3 4 5 6 7 8 9 10
number of sessions
Equation
y = 10x
Meaning:
Each session
costs $10
X
y = mx
15 = m(3)
y = 5x
y=5·6
y = 30
Y
Human years age
A 3 year old cat is often
considered to be 15 in
human years. Assume
that the equivalent age
in human years (y)
varies directly with its
age as a cat (x).
Write and solve a
direct variation
equation to determine
the human age of a cat
that is 6 years old.
40
35
30
25
20
15
10
5
0
2
4
6
8
cat’s age in years
10
y = 30 a cat that is 6 years old is
equivalent to a human that is 30
years old
X
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