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Percents and Proportions. 2.2. Also called Capture-Recapture. . Equation. You HAVE to MEMORIZE this!. The 100 is built into the equation, and will never change. You will be asked to find one of the other pieces (%, part or whole). Method.
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Equation You HAVE to MEMORIZE this!
The 100 is built into the equation, and will never change. • You will be asked to find one of the other pieces (%, part or whole)
Method • Plug in all the information you know into the correct location. • Write a variable (letter of your choice) where there is a blank spot • Cross multiply to solve for the variable.
Example 1 • There are 2500 fish in a lake and 200 of them are tagged*. What percent of the fish are tagged? • Where is the variable going to go in the equation?
Equation Percent=p Part=200 Whole=2500
Cross Multiply 8% of the fish are tagged.
Example 2 • In a bag, 250 pieces of candy are red, and the label says 11% are red. How many pieces of candy are in the bag?
Equation %=11 Part=250 Whole=? = w
Solution • w=2272.7 • Can you have 0.7 pieces of candy? • There are 2272 pieces of candy in the bag.
Example 3 • 113% of 28 is what number?
Percent=113 • Whole=28 • Part=?=p
Solution • 3164=100p • P=31.64
You try! • What percent of 20 is .4?
Percent=?=p • Whole=20 • Part=.4 P=2. .4 is 2% of 20.
Homework • 2.2 worksheet: Skip #1.