# Section 8.1 - Percents

• Definition: Percents represent numbers as part of
100

• Converting Fractions to Decimals to Percent:

1. Divide the fraction, it is now a decimal.

2. Move decimal point two places to the right (multiply by 100)

3. Tack a % sign onto the end

Example (Checkpoint 1): 1/8 = 0.125 = 12.5%

Example (Checkpoint 2): 0.023 = 2.3%

• Converting Percent to Decimals

1. Move the decimal point two places to the left (divide by 100)

2. Remove away the percent sign

Example (Checkpoint 3a): 67% = 0.67

•Percentages are used frequently in Application Exercises

Example (Checkpoint 4): In England, the average price per gallon of premium gas
is $4.30. Of

this amount, $3.44 is for taxes. What percent of fuel cost is for taxes?

Solution:

• Recall that “of” in math is multiplication. To find percent “of” a
number, change the percent to a

decimal and multiply

Example (Checkpoint 6): Each year 8000 Americans suffer spinal cord injuries.
13% of these are

due to sports injuries. How many spinal cord injuries are due to sports injuries
each year?

Solution: 13% of 8000 = 0.13 (8000) = 1040 injuries due to sports

•Definition: Sales Tax is a tax rate (as a percentage) times purchase
price

Example (Checkpoint 7): What is the total price of an item for $1260 if the
sales tax is 6%?

Solution:

price + tax = 1260 + 6% of 1260 = 1260 + 0.06 (1260)

= 1260 (1 + 0.06) = 1260 (1.06) = $1335.60

• Definition: Discounts are percentage amounts taken off of the sales
price

Example (Checkpoint 8): A CD player is originally $380, with 35% off. Find the
purchase price

Solution: original price – discount = 380 – 0.35 (380) = 380 (1 – 0.35) = $247

•Definition: Percent increase/decrease is used to
compare changes

It is found with the formula:

A positive result indicates an increase, and a negative result indicates a
decrease.

Example (Checkpoint 9): Sales went from 1.7 billion in 1998 to 2.2 billion in
1999. What is the

percent increase?

Solution: