This study guide provides an overview of topics to be covered on an upcoming math test on percents. It includes converting between percent, decimal, and fraction forms. Methods are outlined for finding the percent of a number, calculating tax and tip amounts, and determining discounts. Examples are provided for each type of percent problem.

1. Name __________________________________________ Date ____________
Polizzi/Woska Math – 6
Study Guide
Math Test
Percents
Topics on Test:
1. Percent to Decimal 6. Finding percent of a number with decimals
2. Percent to Fraction 7. Tax
3. Fraction to Percent 8. Tip
4. Decimal to Percent 9. Discount
5. Finding percent of a number with proportions
 Percent to Decimal
To change a percent to a decimal, divide the percent by 100  move decimal two places to the left
14% = .14 45% = .45 3% = .03 36.2% = .362
 Percent to Fraction
To change a percent to a fraction, write the percent as a numerator and 100 as denominator,
then simplify to lowest terms
99 50 1 42 21
99% = 50% = = 42% = =
100 100 2 100 50
 Fraction to Percent
To change a fraction to a percent, divide the numerator by the denominator, then move the decimal two
places to the right. Or, when possible, change the fraction to make a denominator of 100, the percent is
now the numerator.
5 7 70 2
= 5  8 = 0.625 = 62.5% = = 70% = 2  5 = 0.4 = 40%
8 10 100 5
 Decimal to Percent
To change a decimal to a percent, move the decimal two places to the right.
0.65 = 65% 0.03 = 3% 1.09 = 109% 0.8 = 80%

2.  Finding percent of a number with proportions
To find the percent of a number using proportions, see how many times the denominator can go into
100 (divide) and multiply the numerator by that amount. The new numerator is your percent.
5
5 x 5 25
= step 1: 20 100 step 2: 5 x 5 = 25 So, = = 25%
20 100 20 100
 Finding percent of a number with decimals
To find percent of a number using decimals, turn the percent into a decimal and multiply by the whole
number.
80% of 40 .80 = 32 75% of 480 .75 = 36
x 40 x 480
32.0 0
600
+ 3000
36.00
 Tax
To find tax, turn the percent (we usually use 8% for tax in class) into a decimal and multiply by the
dollar amount. Then, add that answer to the original dollar amount.
Find the tax on an item that costs $21.00.
21.00 21.00
x .08 The tax is $1.68. + 1.68 The total cost will be $22.68.
1.6800 22.68
 Tip
To find tip, you use the same method that you would for finding tax. Turn the percent into a decimal
and multiply by the dollar amount. Then, add that answer to the original dollar amount.
If you wanted to tip your server 15% on a bill that is $32.50, how much would you be spending on your
dinner?
32.50 32.50
x .15 The tip will be $4.88. + 4.88 The total amount you will spend is $37.38.
16250 34.45
+ 32500
4.8750
 Discount
To find discount, turn the percent into a decimal and multiply by the dollar amount. Then, subtract
your answer from the original dollar amount.
A shirt that costs $38.00 is on sale for 20% off. How much will you spend?
38.00 38.00
x .20 The discount will be $7.60. - 7.60 The total cost will be $30.40.
7.6000 30.40