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
-4550
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
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