PERCENTS

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1. Percent Formula

Part = Percent X Whole

Example: What is 32% of 25?                            Setup: Part = .32  X  25

Example: 15 is 12% of what number?                  Setup: 15 = .12  X  Whole

Example: 25 is what percent of 7?                      Setup: 25 = Percent  X   7

2. Percent Increase and Decrease

To increase a number by a percent, add the percent to 100 percent, convert to a decimal, and

multiply.   To increase 60 by 25 percent, add 25 percent to 100 percent, convert 125 percent to 1.25, and multiply by 60.      1.25 X 60 = 75.

3. Finding the Original Whole

To find the original whole before a percent increase or decrease, set up an equation. Think of

the result of a 17 percent increase over x as 1.17x.

Example: After a 75 percent increase, the population was 5,879. What was the population before the increase.  Setup: 1.07x = 5,879

4. Combined Percent Increase and Decrease

To determine the combined effect of multiple percent increases and/or decreases, start with 100 and then combine.

Example: A price went up 12 percent one year, and the new price went up 24 percent the next year. What was the combined percent increase?

Setup: First year: 100 + (12 percent of 100) =112.

Second year:   112 + (24 percent of 112) = 139.

That’s a combined 39 percent increase.

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