PERCENTS
COMMON MISTAKES
1
10/20/2009
Percents – Convert Percents to Decimals
How to Change Percents
to Decimals
 To convert a percent to a
decimal, move the decimal
point in the percentage two
places to the left.
Common Mistakes
 Moving the decimal point in
the percentage two places to
the right.
 Not moving the decimal
point two places.


Incorrect
0.45% ≠ 45
5% ≠ 0.5
Correct
0.45% = 0.0045
5% = 0.05
2
Complete Manual: ..\Percent Review.docx
To view; right click and open the hyperlink
Percents – Convert Decimals to Percents
How to Change Decimals
to Percents
 To convert a decimal to a
percent, move the decimal
point in the decimal number
two places to the right.
Common Mistakes
 Moving the decimal point in
the percentage two places to
the left.
 Not moving the decimal
point two places.


Incorrect
36 ≠ 0.36%
0.5 ≠ 5%
Correct
36 = 3600%
0.5 = 50%
3
Complete Manual: ..\Percent Review.docx
To view; right click and open the hyperlink
Percents – Convert Percents to Fractions
How to Change Percents
to Fractions
 To convert a percent to a
fraction, divide the
percentage number by 100.
 Reduce and/or adjust as
necessary.
Common Mistakes
 Not reducing or adjusting a
percentage number
containing a decimal point.

Incorrect
45.2
100
Mistake : Fraction is not reduced or adjusted.
45.2% =

Correct
45.2% =
45.2 45.2 10 452 113
=
× =
=
100 100 10 1000 250
Note: Fraction must NOT
contain a decimal.
4
Complete Manual: ..\Percent Review.docx
To view; right click and open the hyperlink
Percents – Convert Fractions to Percents
How to Change Fractions
to Percents
 To convert a fraction to a
percent, first convert the
fraction to a decimal. Then
convert the decimal to a
percent.
Common Mistakes
 Not converting the decimal
to a percent.
 Converting a fraction
incorrectly to a decimal.
 Not moving the decimal
point two places to right.


5
Complete Manual: ..\Percent Review.docx
To view; right click and open the hyperlink
Incorrect
Correct
5
≠ 1.25%
4
3
3
≠ 133.33% (Since ≠ 1.33...)
4
4
7
= 0.875 ≠ 8.75%
8
5
= 1.25 = 125%
4
3
= 0.75 = 75%
4
7
= 0.875 = 87.5%
8
Percents – Percent Equation
How to Solve the Percent
Equation
 The statement
A is p% of B
results in the equation
A = (p/100)×B
 Remember “is” means equals
and “of” means to multiply.
6
Complete Manual: ..\Percent Review.docx
To view; right click and open the hyperlink
Common Mistakes

Inputting the wrong values
into the equation.

Incorrect
50 is what percent of 940?
A = 50% × 940
15% of what is 39?
A = 15% × 39

Correct
50 is what percent of 940?
50 = p % × 940
p
50 =
× 940
100
100
× 50 = p
940
p = 5.3%
15% of what is 39?
15
× B = 39
100
100
B = 39 ×
15
B = 260