1. Percent
Lesson 53

2. The word percent can be broken down to determine its meaning.
per = by cent = one hundred
Therefore, the word percent means by 100.
The symbol for percent is %

3. One percent of a number is one hundredth of the number.
Therefore, 20 % means 20 parts of 100 or 20 hundredths.

4. Percents have equivalents in both fractions and decimals
Reduced
Percent
Decimal
Fraction 1 5
20%
.20 20
100 = = =

5. How to find a percent of a whole number
Don’t forget that “of” means to multiply of x =

6. How to find the percent of a whole number.
Step 1 - When you see a percent problem you know when you read “of” in the problem you multiply.
25% of 200

7. Step 2 – Change your percent to a decimal and then move it two places to the left.
25% x 200

8. Step 3 – Multiply just like a regular decimal multiplication problem.

9. Step 4 – Place the decimal point 2 places to the left in your answer.
5000

10. What is 20 % of 820?

11. Example
What is 40 % of 725?

12. Example
What is 60 % of 692?

13. Example
Sales tax is 5% in Maryland. Joey bought a pair of basketball shoes advertised for $ How much sales tax did he pay?

14. What does increase in % mean?
What if you heard that the price of peanuts in Beijing went up 10% last year. If the old price was 60 yuan, what is the new price?
What is 10% of 60 yuan?
0.1 x 60 = 6 yuan ( this is the increase)
Now add the increase to the old price:
= 66 yuan

15. Practice: Try this on your own!
The number of acorns on the ground increased 240 percent during the storm. If 5400 acorns were on the ground before the storm, how many were on the ground after the storm?
240% x 5400 = b
2.4 x 5400 = 12960
= 18,360 acorns

16. Percent of Increase
To find a percent of increase, form a fraction with the amount of increase over the original amount, and change the fraction to a percent.

17. Percent of Decrease
To find the percent of decrease, follow the procedure for finding a percent of increase, but place the amount of decrease over the original amount.

18. Example
In 2000, there were 240 eighth graders enrolled in Sachin’s school. In 2005, there were 336 eighth graders enrolled. What was the percent of increase in enrollment?

19. Answer 1st: find the amount of increase: 336-240 2nd: form a fraction
amt. of increase = 96
original amt
Change the fraction to a decimal
Change the decimal to a percent

20. Example
Zack Cole shot an 86 on the golf course on Monday. On Friday, he shot a 95. What is the % of change?

21. Homework 1 What is 1% of 24? What is 56% of 24? What is 1% of 3200?
75% of all the skateboarders at the competition could execute a kickflip. If 14 could not execute a kickflip, how many skateboarders were at the competition?

22. Homework 2
The ratio of western movies to comedies at the video store was 7 to 9. If there were 210 westerns, how many comedies were there?
Thirty percent of what number is 123?
What percent of 39 is 24?
There are 130 mountain bikes at Ike’s Bikes bicycle shop. If 52 of the mountain bikes have bar ends, what percent of the bikes have bar ends?

23. Homework 3
The number increased from 40 to What % increase was this?
Jonathan Rogers drew 47 planes in 4th period. He drew 28 in 5th period. What is the % of change?
Matt Viers bought 42 CD’s last year. He bought only 35 this year. What is the % of change?
Last six weeks, Joseph Lawhorn made an 88. This six weeks he made a 92. Find the % of change.