 So there are 55 students in a class, 25 of them work 20 hours a week or more at jobs outside of school. What percent of the students work 20 hours or more per week at jobs? So we're looking for the percent of students. So what do we know? We know that there are a total of 55 students in this class and we know that 25 of them are working 20 hours or more a week. So first we can set up just a fraction to represent this or a ratio to represent this. So 25 out of 55 students are working. So 25 students are working 20 hours a week or more out of 55 students that are the total number of students in the class. So again you have two options of how you can do this. First I could change this fraction to a decimal. So 25 divided by 55 would give me approximately 0.45 and then remember we can then change that decimal to a percent by moving the decimal point two places to the right. So that would give me 45 percent. So this is method one. And this means that 45 percent of the students in this particular class work 20 hours a week or more. Now let's look at method two. The other option would be to take the same 25 out of 55 students and set up a proportion and remember because we're talking about a percent it's going to be something which I don't know out of 100. And to solve this we just cross multiply. So 25 times 100 would be 2500. Set it equal to 55 times x which is 55x. And again to solve we're just going to divide by sides by 55. So 2500 divided by 55 will give us again about 45 percent is equal to our value. So in both cases we end up with 45 percent. One more example. Osteoporosis is a disease that leads to brittle bones and is partially caused by a lack of calcium. Each year 250,000 people suffer osteoporosis related hip fractures. About 15 percent of whom die after sustaining such fractures. How many people die each year after fracturing their hip? So there are two numbers that we need to focus on. The first one we're talking about a total of 250,000 people who suffer from hip fractures. And then we're given that 15 percent of those die. So let's see if we can write this into a problem that makes a little more sense written out in words. So it's really 15 percent of how many die well out of a total of 250,000. So 15 percent of the total is going to be the number that die. And this goes back to one of our rules. First thing, you want to take the 15 percent and change it to a decimal. So remember right now, 15 the decimal places here, move it two places to the left, and we end up with 0.15. Then remember the word of implies multiplication. And then finally just drop down the 250,000. So it becomes a very simple multiplication problem. So 0.15 times 250,000 will give us a total of 37,500 of those who suffer from a hip fracture that will die. So that sums up for cents.