So you want to do conversions. You want to write a measurement that was in one set of units in a different set of units. And so to do conversions well, you need two things. The first one is a conversion factor. And so these are your open one statements. With these conversion factors, those will be given to you in an example. And so you don't need to memorize the ideas. I want to see that you know how to apply them. Another thing you need is to make sure that your units cancel correctly. So units must cancel correctly. So what I found is that students who are just starting doing conversions oftentimes multiply everything together really quickly in their calculator or divide everything really quickly. And then the answers they get, the units may not cancel correctly and they get the wrong answer. And so this is going to be important because later this semester we'll be doing long strings of conversion factors to get different results. And so it's important now that you show your work and you make sure your units cancel correctly. So as an example, I want to go through these two questions. How many inches are in 75 centimeters and how many feet? So to do this, the first thing we'll need is our conversion factor. So we can say in one inch there are 2.54 centimeters. Now we can write that saying one inch has 2.54 centimeters or we can write there are 2.54 centimeters in one inch. So these two are equivalent. It's just two different ways of saying the same thing. So when we start the problem, we want to always begin with whatever information was given in our problem statement. So we'll start with saying we have 75 centimeters and we're looking to see how many inches is that. So this is what we're trying to solve. So to do that, we'll again start with our 75 centimeters and now we need to multiply by one of our conversion factors. And so if we have 7 meters in the numerator here, we're going to need to multiply by one of the conversion factors that has 7 meters in the denominator. So that way, that is in the top cancels, what's in the bottom and we're left with inches. So we'll use this conversion factor to do that. We say in one inch or 2.54 centimeters. So now if we multiply all of this out, we would say 75 times one divided by 2.54 is 29.7. And we can see here that the centimeters cancel and then we're left with inches. 29.5. So now going onto the next part of the question, it says how many feet are in 75 centimeters? We don't know a direct conversion factor that goes from centimeters to feet. So instead, we'll go centimeters to inches and then inches to feet. So we've already have inches here and so now we need to look for a conversion factor to go from feet to inches. And now to saying that in one foot there are 12 inches. So we could write that like this or we could write there are 12 inches in one foot. So those are the two ways we could write that. And now going from here, 29.5 inches. We need to choose the conversion factor that will cancel inches and leave us with feet. So we'll choose this conversion factor. So we'll recent a 1 foot over 12 inches. So we'll multiply 29.5 times 1 and then divide it by 12. And we'll get 2.468. And so the inches cancel and the only unit we're left with is in feet. So we can also notice that our first are given information have 3 significant digits. And our answer in inches and in feet also have 3 significant digits. So these conversion factors are exact, which means that 1.0, 0, 0, 0, 0, 0, 0 for ever inches is 2.54, 0, 0, 0, 0, 0, 0 for ever centimeters. So these conversion factors do not affect your significant figures, only the given information. So this is one way how you can solve it, sort of doing it step wise. If you wanted to go from centimeters to feet, we could do that all at once. I'm saying 75 centimeters. And so this is one inch over 2.54 centimeters. And then multiplying that, 1 foot over 12 inches. And so the centimeters cancel. The inches would cancel and all we're left with is feet. We would say 75 times 1 times 1. And divided by 2.54 divided by 12, we would get the same answer. 2.468.