Calculations with Percents

36%

64%

45%

90%

85%

.7%

12%

8%

57%

10%

Review:O Change a fraction to a decimal:

O Divide the numerator by the denominator.

O Example: Change 5/9 to a decimal.O 5 ÷ 9 means

9 5.000

O 5/9 = 0.55 or 0.56

0.5-45

50

5

-4550

5

Review:O Change a decimal/number to a percent:

O Move the decimal two places to the right. (Multiply by 100).

O Example: Change 0.683 to a percent.O 0.683(100) = 68.3%

O Change a percent to a decimal/number:O Move the decimal two places to the left.

(Divide by 100).O Example: Change 3% to a decimal.

O 3 ÷ 100 = 0.03

You cannot do any math problems with percents. You must change the percent to a decimal.

Finding a Percent of a Number

O What is 25% of 32?O Step 1: Change English to Math.

O What is your variableO IS is your = signO Change your percent to a decimalO OF means multiply

O x = .25(32)O Step 2: Decide how to solve the

problem, then solve.O x = 8O 8 is 25% of 32.

Finding the Percent One Number is of Another

O What percent of 120 is 90?O Step 1: Change English to math.

O What is your variableO OF means multiplyO IS is your = sign

O x(120)=90O Step 2: Decide how to solve the

problem, then solve. O x = 90÷120 = 0.75

O Step 3: Change your answer to a percent.

O x = 75% 75% of 120 is 90.

Finding a Number when the Percent is Known

O 36 is 4% of what number?O Step 1: Change English to Math.

O IS is your = signO Change your percent to a decimalO OF means multiplyO What is your variable

O 36 = 0.04(x)O Step 2: Decide how to solve the problem,

then solve. O 36÷ 0.04 = xO x = 900O 36 is 4% of 900

Practice:1. What number is 44% of 6?

2. 125 is what percent of 1250?

3. 32 is 25% of what number?

2.64

10%

128