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Practicing With Percents
By Johnny, Sally, Mary & Joey
Period 3
What is a Percent?
Percent means “out of 100”
11% means 11 out of 100
Example: If 11% of people liked a movie, that means that 11 people out of every 100 will say they like the movie.
Converting to Percents from…
…a decimal -- move the decimal point _____ spaces to the right and add a percent sign (%)
0.83 = 83% 1.45 = 145% 0.385 = 38.5%
•…a fraction - divide numerator by denominator (like a test grade) to make a decimal. Then, follow the rule above.
0.2 =20%1
5= 3
8= 0.375 =37.5%
Converting from Percents…
…to a decimal - move the decimal point ____ places to the ____ and drop the percent sign
14% = 0.14 2.5% = 0.025
•…to a fraction - drop the percent sign and put the number over 100. Then, simplify the fraction
14% =14
100=
750
2.5% =2.5
100=
251000
=140
Solving Percent Problems
We need to use a _________ to solve percent problems
%
100=
isof
or%
100=
partwhole
Example 1
What is 12% of 45?12
100=
x45
540 =100x
5.4 =x
Set up the proportion
Cross multiply
Solve the one step equation by dividing
Example 2
213 is 35.5% of what number?
Set up the proportion
Cross multiply
Solve the one step equation by dividing
35.5
100=
213x
21300 =35.5x
600 =x
Example 3
What percent of 36 is 1.8?
Set up the proportion
Cross multiply
Solve the one step equation by dividing
x
100=
1.836
180 =36x5 =x5%
Real World Example
QuickTime™ and aH.264 decompressor
are needed to see this picture.
Quick Quiz
1. Find 11% of 68
2. What percent of 475 is 285?
3. 98% of what number is 24.99?
4. Convert 84.5% to a fraction and a decimal
5. You want to buy a shirt that is $25.99 and is on sale for 25% off. How much will you pay?
Answers: 1. 7.48 2. 60% 3. 25.5 4. 0.845 5. $19.49 169
200
