Math Symbols are
a communication
tool. Symbols are an
invention which is
used to eliminate
the need to write
long, plain language
instructions to
describe
calculations and
other processes.
To understand
the % sign, ask
yourself the
following four
questions:
(1)
What
does the % sign
mean?
. . .
A
%
is used
to
compare
a
number
(any
number)
to
100
using
division.
Under normal
circumstances,
all
numbers are
compared to
the number 1
using
division.
For example,
the number 3 is
only a 3 when
it is compared
to the number 1
using
division.
It is three
times as big as
the number
1.
However, a %
does not use
the number 1
for comparison
purposes.
A %
is used to
compare
a number
(any number)
to
100
using
division.
Continuing on
with the number
3 compared to
the number 1 as
an example, the
result is:
(Note that the
quotient must
still equal 3.
The number 300
is three times
as big as
100.)
The final
percentage
is:
3 =
300%
. . .
Any
Number
can be
converted to a
percent
You can
complete a
short
calculation
similar to the
example shown
above, or . .
.
. . . Just move
the decimal
point to the
right by two
places.
(2)
Where
is a % symbol
used?
. . .
A %
symbol is
only
used to
represent a
proportion.
A
percent tells
you that you
are dealing
with a
ratio
, or relative
comparison
(using
division).
Although any
number can be
converted into
a %, percents
are only used
to represent
ratios
(proportions).
. . .
What is
the
point of
converting
a ratio to a
%
?
Is there any
advantage to
saying 5.6%
instead of
.056?
Read on . .
.
(3)
How
is a % symbol
used in
everyday
life?
. . .
There are
thousands
and thousands
of
applications
where the
concept of a
percent is used
every day.
The fact that a
percent
represents a
proportion (a
relative
comparison) is
what makes
valuable.
Here are some
common
examples
:
. . .
Sales
Tax
. . .
When you pay a
sales tax, the
tax rate will
be stated as a
%
.
If the sales
tax rate is 8%,
this means that
you will pay
the government
a tax of 8
dollars
for
every
100
dollars you
spend.
If you spend
$100, you owe a
tax of $8. If
you spend $200,
you owe tax of
$16. If you
spend $50, you
owe a tax of
$4. If you
spend $25, you
owe a tax of
$2, and so on.
The sales tax
you owe is
always the same
proportion of
what you spend
(in these
examples it is
8% of what you
spend).
. . .
Bank
Interest
. . .
If you deposit
money in a
bank, the
interest the
bank will pay
on your account
will be stated
as a
%
.
If the interest
rate is 5%
(simple annual
interest), this
means that the
bank will pay
you 5 dollars
for
every
$100 you
leave in your
account for one
year.
If you leave a
$100 deposit in
the bank for
two years, you
will receive
$10 ($5 per
year). If you
leave a $100
deposit in the
bank for only
six months, you
will receive
$2.50, and so
on. The amount
your deposit
earns is always
the same
proportion.
. . .
Credit
Card
Interest
. . .
If you use a
credit card,
the interest
you pay on the
outstanding
balance you owe
will be stated
as a
%
.
If the interest
rate is 20%
(simple annual
interest), this
means that you
pay the credit
card company an
extra 20
dollars per
year
for
every
$100 of
unpaid
debt.
. . .
Test
Grades in
School
. . .
Test grades in
school are
often stated as
a %
.
If a student
has a test
average of 81%,
this means that
for
every
100
questions the
student answers
on his or her
tests, 81
questions are
answered
correctly.
. . .
Slope of
a railroad
track
. . .
Slope (the
incline of the
tracks) is
often stated as
a %
.
If a slope of a
railroad track
is a 5% grade,
this means that
for
every
100 feet
of horizontal
distance the
tracks drop (or
increase) 5
feet in
elevation.
. . .
Survey
(Poll)
. . .
Survey results
are often
stated as a
%
.
If a survey
found that 75%
of restaurant
patrons
preferred a
certain type of
food, this
means that
for
every
100
people, 75
people prefer
that type of
food.
(4)
What
math
symbols can be
mistaken for a
% sign
?
. . .
Per
mille .
. . 
. . . The
Per mille
symbol is
not
equivalent
to a
Percent
symbol.
1 % (percent)
means 1 part in
100.
1 
(per
mille)
means 1
part in
1000.
. . .
Basis
point .
. . 
. . . The
Basis point
symbol is
not
equivalent
to a
Percent
symbol.
1 % (percent)
means 1 part in
100.
1 
(basis
point)
means 1
part in
10,000.
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