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Math 1650 Lecture Notes
§1.11
Jason Snyder, PhD.
Modeling Variation
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of
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§
1.11: Modeling Variation
Direct Variation
Example 1
Direct Variation
During a thunderstorm you see the lightning before you hear the thunder because
light travels faster than sound.
The distance between you and the storm varies
directly as the time interval between the lightning and the thunder.
(a) Suppose that the thunder from a storm 5400 ft away takes 5 s to reach you.
Determine the constant of proportionality and write the equation for the variation.
(b) Sketch the graph of this equation. What does the constant of proportionality
represent?
(c) If the time interval between the lightning and thunder is now 8 s, how far
away is the storm?
?
=
°?
Direct Variation
If the quantities
x
and
y
are related by an equation
for some constant
k
0
, we say that
y
varies directly as
x
, or
y
is
directly
proportional to
x
, or simply
y
is proportional to
x
.
The constant
k
is called
the
constant of proportionality
.
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This note was uploaded on 10/07/2009 for the course MATH 150 taught by Professor Unknown during the Spring '06 term at Ohio State.
 Spring '06
 UNKNOWN
 Math, Direct Variation, Inverse Variation

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