 Okay, let's go ahead and check out this next example. This one is the experiment that you see done at the beginning of the movie Raiders of the Lost Ark by Indiana Jones when he's in the temple in Peru or whatever. He's trying to replace the golden statue with the bag of sand on that weight sensor and we're going to see here if that's a plausible experiment to do. So we see the volume of both of these items is the same at 1.75 liters and the problem actually gives you the density of both gold and sand. So you're going to need to use those densities as conversion factors within the problem. And I've also put the other three conversion factors that you need in this problem to do it the way I'm doing it. So the first part of the problem says well what's the mass of both of these items? So the ultimate problem really is converting volume to mass or in our case liters to kilograms to be specific about it. So the mass of the gold, well you're going to start with the volume of the gold, cancel out those liters. So you're going to find the conversion factor that has the liters in it and so that's going to convert those liters to milliliters and then we're going to cancel out those milliliters using the next conversion factor, the cubic centimeters. So now we're in cubic centimeters. Now we can go back to the density and use that as a conversion factor to get from cubic centimeters to grams and I've done one more step to convert it from grams to kilograms because kilograms to me is easier to use especially in those big numbers as opposed to grams like I can wrap my brain around that number a little easier. So we do that same calculation with sand converting liters to milliliters then converting milliliters to cubic centimeters then going back and using the density as the next conversion factor to convert cubic centimeters to grams and then again converting that grams to kilograms. So both of those answers should be in three sig figs because of the volume of the objects. That was the given in the problem so we're going to go with the given as our significant digits and remember your units as well. So of course already you should be able to see that the difference in mass of those two items is fairly significant so he's going to go ahead and set off the alarm I guess for the viewers in the United States if you're having a hard time with those kilograms right that's about I don't know around 75 pounds for the mass of the statue and about 12 pounds for the mass of the sand so you can imagine well even imagine back to the movie and remember him trying to grab that with or grabbing that and lifting it up with one hand so that's pretty tough but anyways obviously he set off the alarm both in our problem and in the movie so I guess that's why the boulder came down so hopefully this makes sense and let me know if you have any questions on it