In this example question, it says the pressure in Denver, Co, which has an elevation of 5280 feet, averages about 24.9 inches Mercury. Now we have to convert this pressure into millimeters of mercury and atmospheres, all right. So this is basically a dimensional analysis type of question. We have to convert from inches mercury to millimeters of mercury. Once we have that, we can then change those millimeters of Mercury into atmospheres.
So let's start out with 24 inches mercury. We want to get rid of inches mercury, so we're going to put inches mercury on the bottom. And then remember that from dimensional analysis, we know there's a relationship between inches and centimeters. So we're going to go from inches mercury to centimeters Mercury. Now recall, if you've looked at my dimensional analysis videos, you know that one inch is equal to 2.54 centimeters. Here are inches Mercury cancel out and now we have centimeters of mercury.
Now we want to get rid of centimeters of mercury, so put it on the bottom and we can go from centimeters to millimeters. And we can say here that one centimeter is 10mm, canceling out everything. What we'll have left at the end is millimeters of mercury, which comes out to 632.46mm of mercury. Now because our values within the question have 3 SIGFIX with 24.9, not 24.9 and three six figs here as well, we're going to put this in three sig figs, so 632mm of Mercury.
Now we want atmospheres, so let's take that 632.46mm of Mercury and we're going to convert that into atmospheres. So remember here one atmosphere is equal to 760mm of Mercury. So when we do that, we're going to get as our answer 0.832 atmospheres as our final answer. So just approach this like any dimensional analysis type of question to convert from one pressure unit to another.