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Variables and constants represent values.
A constant is a value that does not change.
A variable is a value that can change.
In science, constants represent attributes
of physical phenomenon. Water freezes at
32F (or 0C). This temperature is a
constant; water always freezes at this
temperature.
The ratio of the circumference of any
circle to its diameter is a constant, namely: ∏.
So, given the diameter of a circle or the
radius of a circle we can always find the
other.
A variable depends upon constants and other
variables. For example, let's say you
have an after school job that pays $6 per
hour. The amount of money you make
depends upon the number of hours you work.
So your pay is variable and so is the time you
work. The 6$ is the constant that
relates the two. If you work 2 hours
then you will bet paid (2 * $6) = $12.
If you work 4 hours your pay will be (4 * $6)
= $24.
The letters a, b, c, ..., o are
conventionally used to name constants.
The letters p, q, r, ..., z are
conventionally used for naming variables.
(Please note, there are exceptions to this
convention.)
Algebraic expressions include constants and
variables. Typically these expressions
are within equations and the fundamental goal
is to rearrange the expressions so that we
arrive at one variable being equal to the
remaining expression of constants and
variables.
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