Name ___________________________________________ Mods ...

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Name ____________________________________________________ Period _____ Percent of Change


1. We can use PERCENTS to describe the amount of change in a quantity over time. Consider this:

• Last year, Denim Dudes sold a pair of jeans for $30. This year, the price of the same jeans was raised to $37.50. The cost of the jeans was changed by what percent?

• There is a very specific way to calculate percent of change. Let’s learn how to do this – then we’ll come back and solve this problem. (


3. What does the formula mean?

• The original amount is the number you had when you started.

• Subtract the two amounts – that’s the difference

• Write a ratio that compares Difference to Original. Fraction form works best.

• Enter the ratio as a fraction into your calculator OR enter it as a division problem.

• Change the answer to a percent. (Either move decimal point to the left 2 places OR multiply by 100)

• Round answers to the nearest percent. Use standard rounding rules.

• Be sure to put a % on your answer!

4. Let’s go back to the Denim Dudes problem from above. Last year, Denim Dudes sold a pair of jeans for $30. This year, the price of the same jeans was raised to $37.50. The cost of the jeans was changed by what percent?

• Original price ________________________________________

• New price ___________________________________________

• Difference ___________________________________________

• Divide difference by original = ___________________________

• Change to a percent = __________________________________ * round to the nearest % if needed*

• Did the price increase or decrease? ________________________

5. Do I REALLY have to write all those steps? ……. _________

Here’s what you must write for every percent of change problem:

• Write the FORMULA (difference over original) and show your substitution.

• Write the percent. (That means do the calculation and put the % after the number.)

• Tell if the change was an increase or decrease.

So that means in #4 above you could have just written:

Practice problems. Find the percent of change. Round answers to the nearest percent and state whether the change was an increase or decrease. I encourage you to use a separate piece of paper to do this work.

6. The temperature dropped from 105○ to 88○.

7. The price of a pair of sneakers is marked down from $44.99 to $35.00

8. Jake’s bowling average went from 145 to 172.

9. In the past five years, the price of a cheeseburger went from $0.72 to $0.80.

10. Michael’s time in the 400-meter dash went from 71 second to 62 seconds.

11. The cost for a child movie ticket went from $4.50 to $4.75.

12. Keith bought a new tent that had a sale price of $20.74. The original price of the tent was $82.99.

13. The Fine Furniture Company paid $325 for a kitchen table and chairs. They sold the table and chairs for $650.

14. A graphing calculator was $60 last year and is now $63.

15. The number of camera club members was 27 last year. This year it is 20.

16. Yesterday, the parents sold 10 tickets to the swimming party. Today they sold 20 tickets.

17. Betty sold 20 boxes of Girl Scout cookies last week. This week she sold 10 boxes.

18. Andy wanted to sell his baseball card collection for $230. He changed the price to $250 when he got lots of offers on his collection.

19. Sarah wanted to sell her Gameboy and all of her games for $180. No one offered to buy them, so she changed the price to $140.

20. For the recycling project, the Bernhardt’s collected 25 pounds of newspapers last year. This year they have collected 18 pounds of newspapers.


Percent of Change = Difference



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