Video and Examples
Before solving a percent problem, you must first identify which numbers represent the PART and which numbers represent the WHOLE.
What is 45% of 40?
In this problem, 45% is the part and 40 is the whole. 100% (even though you don't actually see the number 100 anywhere) is also the whole. So, we are looking for the part that 45% is equal to. A proportion would look like this...
Now you can solve the problem using any method you choose.
Remember: Percent means "per hundred", so in every percentage problem you solve, something will always be compared to 100.
Often times when solving a percentage problem, you will need to identify two equivalent ratios, one of which will be a ratio involving "100".
Directions:
 In this applet, begin by selecting the value of 100% (the whole) with the red slider.
 Slide the green point to the left and right to select the percentage (the part) of the whole.
 Observe how the three solution methods are related to each other and to the percent bar.
Try using this applet to solve these questions...
 If 80 is 100%, how much is 75%?
 If 160 is 100%, what percentage is 48?
 If 65% is 104, how much is 100?
Try these practice problems. Click the [show anwer] to check your work.
EXAMPLE 1 In a parking lot with 250 parking spaces, 40% of them are vacant. How many spaces are occupied? 
[show answer] 
EXAMPLE 2 A computer normally costs $600, but it is on sale for 35% OFF.

[show answer] 
EXAMPLE 3 On a test you got a 34/40. What percent of the problems did you answer correctly? 
[show answer] 
EXAMPLE 4 Jon has 12 stamps with boats on them. This is 40% of his collection. How many stamps are in his entire collection? 
[show answer] 
SelfCheck
Question 1 Each year Charlotte donates 5% of her income to charity. If she donated $3000 last year, what was her total income? 
[show answer] 
Question 2 Tracy's soccer team scored 80 goals this year. Tracy scored 30% of those goals. How many goals did Tracy score? 
[show answer] 
Question 3 In a survey, 18 out of 24 people preferred Joe's Burgers over Patty's House of Burgers. What percent is this? 
[show answer] 