Percent is out of 100
Percent sign % is used to indicate the number in parts of 100.
Fraction and decimals can be represented as percents,
Expressing a fraction as a percent
Ex. Express 5/8 as a percent.
Step 1. Divide the numerator by the denominator 5/8 = .625
Step 2 – multiply the quotient by 100 = 62.5
Step 3 add the percent sign 62.5%
1/8 = .125
.125 X 100 = 12.5
12.5%
Expressing a decimal as a percent
Express .47 as a percent
Step 1. Move the decimal place 2 places to the right. ( multiply by 100) .47 x 100 = 47
Step 2. Add percent 47%
Ex. .023 (100) = 2.3 = 2.3%
Expressigng a percent as a decimal
Express 180% as a decimal
Move decimal two places to the left
Percent change
Percent increase = Amount of increase / original amount
Percent decrease – Amount of decrease/original amount
a. If 6 is increased to 10. Find the percent increase.
4/6 = .67 x 100 = 67% increase
b. If 10 is decreased to 6, find the % decrease
4/10 = .4 x 100 = 40%
Rounding percents when necessary
Divide, carry the decimals to 4 decimal places, round to 3 decimal places.
Ex. Find the percent increase from 7 to 11
11-7/ 7 = 4/7 = .5714 round to .571 x 100 = 57.1%
Reg prices 135, sale price 60.75
Find % decrease
135-60.75/135 = .55 x 100 =55%
Tv reg 940, sale price 611
940-611/940 =.35 x 100 = 35%
Percents, sales tax & discounts
A= P*B
A is a percent of B
Calculating sales tax
Sales tax = Tax * items cost
Ex. 4 Sales tax is 7.6, purchase bike for $394
a. How much tax? Drop % and move decimal two to left.
.075 * 394 = 29.55
b. Total for bike and tax = price + tax = 394 + 29.55 = 423.55
Ex. 5
Sales tax is 6%, you buy a computer for $1260
a. How much tax is paid? .06 * 1260 = $75.6
b. How much is final cost of computer? Tax plus price = $1335.6
Calculating discounts
Discount = discount rate * original price of the item.
Example 5.
A computer with the price of %1460 is on sale for 15% off.
a. What is the discount amount? 1460 * 15%. Drop percent and move decimal two places
to the left. .15 *1460 = $219
b. Total price for computer = price minus discount 1460- 219 = $1241
Ex. 6
You are purchasing a cd player with an original price of $380 that is on sale for 35% off.
a. What’s the discount amount? $380 .35 =$133
b. What’s the final cost? $380.35-133 = $247