Walton CSD



Name:____________________________________Desk #:____________Lesson 5.1 – Percent Increase and DecreaseFind the Percent of a NumberWhen you want to find the percent of a number, turn the percent into a decimal (move the decimal two places to the left). Then, multiply the decimal you got by the number you are finding the percent of.For example, to write 30% of 45, we do:30% = .30451279133143196 x .3 13.5Examples:50% of 64 7% of 30 6% of 1000 32% of 62 359952213027500Finding Percent IncreasePercents can be used to describe how an amount changes. The change may be an increase or a decrease. Percent increase describes how much a quantity increases in comparison to the original amount.Example 1:Amber got a raise, and her hourly wage increased from $8 to $9.50. What is the percent increase?Step 1: Find the amount of change.Amount of Change = Greater Value – Lesser Value = ________ - ________ = __________44178925417800Step 2: Find the percent increase. Round to the nearest percent. = = ___________ ≈ ____________Amber’s hourly wage increased by ______________a. What does a 100% increase mean? ___________________________________________________________________b. The price of a pair of shoes increases from $52 to $64. What is the percent increase to the nearest percent?Finding Percent DecreaseWhen the change in the amount decreases, you can use a similar approach to find percent decrease. Percent decrease describes how much a quantity decreases in comparison to the original amount.Example 1:David moved from a house that is 89 miles away from work to a house that is 51 miles away from work. What is the percent decrease in the distance from his home to work?Step 1: Find the amount of change.Amount of Change = Greater Value – Lesser Value384746512700Calculator Tip!In your calculator to find percent change:(Greater Value – Lesser Value) ÷ Original Amount020000Calculator Tip!In your calculator to find percent change:(Greater Value – Lesser Value) ÷ Original Amount = ________ - ________ = __________44178925417800Step 2: Find the percent decrease. Round to the nearest percent. = ≈ ___________ ≈ ____________David’s distance to work decreased by ______________.a. The number of students in a chess club decreased from 18 to 12. What is the percent decrease? Round to the nearest percent.b. Pencil Police Officer Jacob wrote 16 tickets for pencil stealing violations last week, but only 10 tickets this week. What is the percent decrease?Using Percent of ChangeGiven an original amount and a percent increase or decrease, you can use the percent of change to find the new amount.Example 3The grizzly bear population in Yellowstone National Park in 1970 was about 270. Over the next 35 years, it increased by about 115%. What was the population in 2005? Round to the nearest whole number.Step 1: Find the amount of change._________ x ________ = __________ ≈ ____________Step 2: Find the new amount.New Amount = Original Amount + Amount Change = ____________ + _____________ = _____________The population in 2005 was about __________ grizzly bears.a. If an amount of $100 in a savings account increases by 10%, then increases by 10% again, is that the same as increasing by 20%? Explain.__________________________________________________________________________________________________b. How can you tell whether a situation involves a percent increase or a percent decrease?____________________________________________________________________________________________________________________________________________________________________________________________________c. A TV has an original price of $499. Find the new price after the given percent of change:10% increase 30% decreaseLesson 5.1 Extra PracticeShow your work on a separate sheet of paper (or on bottom of page 6). ................
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