 Okay, this problem is nice to get us started because it shows us how to do these simple one-step conversions. So on the right of the page, next to each one of the four problems, I have written the conversion factor that you need to convert from one unit to another. So the first set of units is inches and centimeters, both distance units, right? So we can convert directly between them, just find the conversion factor, which is given to us. So we take that 40.0 centimeters, arrange the conversion factor in the appropriate way, putting the centimeters on the bottom and the inches on the top, canceling out the centimeters and going to three significant figures because 40.0 has three significant figures. Okay, we're going to do the same analysis, use the same problem solving strategy for the rest of the problems. So we have the unit conversion, one meter equals 3.28 feet. And now we're going to do dimensional analysis, 27.8 meters, multiply that by the conversion factor with the meters in the bottom. Meters cancels out, so we're going to effectively multiply 27.8 times 3.28 feet, and we're going to get 91.2 feet to the correct number of sig figs. So the number matters, the significant figures matter, and the units matter. You have to remember to put all of those in your answer. Okay, so let's go to C now, 10 kilometers. We're going to cancel out the kilometers by putting it on the bottom, using the conversion factor on the right, 0.621 miles on the top. So we're going to multiply that by 10, giving us 6.21 miles to the right number of sig figs. Lastly, D, 3,845 kilograms, we're going to use that conversion factor found on the right. One kilogram equals 2.205 pounds. So we're going to put 2.205 pounds on the top and one kilogram on the bottom because we want to cancel that kilogram units out. And when we do that, we get 8,478 pounds and make sure you go to the right number of significant digits. There's four in the original number, so there has to be four in the answer. Okay? Let me know if you have any issues on that one.