6.5: Percent of Increase or Decrease

6.5: Percent of Increase or Decrease

Thursday 2/25/21

In today's lesson, you will be finding what is called the percent of change between two values or the amount of percent by which an original amount increases or decreases by. There are "two formulas" you will be dealing with, but the only change between them is how you subtract in the numerator.

Essentially, to find the percent of change, you subtract the original and new amounts so you get a positive difference. You then ALWAYS divide by the original value.

An increase occurs when the new value is larger than the original.

A decrease occurs when the new value is less than the original.

In the first example, you will see a percent of increase, where the new amount is larger than the original amount. Before you proceed, be sure to copy down both formulas from the third slide.

Now, you will try one on your own. Be sure to go back and check over the example again if you need to before going on to the Checkpoint Example.

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Checkpoint Example 1

Find the percent of increase from 10 inches to 18 inches.

Be sure to include the percent AND the word increase in your answer.

Sample: 125% increase

In the next example, you will be finding a percent of decrease, where the new amount is less than the original amount.

Now, you will try one on your own. Be sure to go back and check over the example again if you need to before going on to the Checkpoint Example.

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Checkpoint Example 2

Find the percent of decrease from 63 inches to 56 inches. Round to the nearest tenth of a percent.

Be sure to include the percent AND the word "decrease" in your answer.

Sample: 28.6% decrease

NOTE: You do not need to write the word "about" in here even though it is being rounded. Just follow the sample above.

The examples that follow will be today's classwork. Before you move on, you can click through the previous slides again to view the examples. I have also posted the notes in the Class Notes Document on Google Classroom. When you are ready, click to the next slide.

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#1

Find the percent of change. Round to the nearest tenth of a percent, if necessary.

50 pounds to 35 pounds

Samples: 10% increase or 10% decrease

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#2

Find the percent of change. Round to the nearest tenth of a percent, if necessary.

24 songs to 78 songs

Samples: 10% increase or 10% decrease

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#3

Find the percent of change. Round to the nearest tenth of a percent, if necessary.

10 gallons to 14 gallons

Samples: 10% increase or 10% decrease

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#4

Find the percent of change. Round to the nearest tenth of a percent, if necessary.

72 paper clips to 63 paper clips

Samples: 10% increase or 10% decrease

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#5

Find the percent of change. Round to the nearest tenth of a percent, if necessary.

18 feet to 26 feet

Samples: 10% increase or 10% decrease

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#6

Find the percent of change. Round to the nearest tenth of a percent, if necessary.

68 miles to 42.5 miles

Samples: 10% increase or 10% decrease