 Aluminum engine block has a volume of 4.77 liters and a mass of 12.88 kilograms. What's the density of the aluminum engine block in grams per cubic centimeter? So the density that we have now essentially, remember what is the formula for density? Anybody? Density equals mass divided by volume. And we have the mass, we have the volume, right? But if we put those in, our density would be in the wrong units. Specifically, it would be in kilograms per liter, right? But we want it in grams per cubic centimeter. So in order to do this, we need to do a couple of conversions. And we've got one of the conversions written up here for us. One milliliter equals one cubic centimeter. And the other two conversions that we need are just metric to metric conversions, OK? So first thing we're going to multiply. So let's get rid of the kilograms, right? So what do we put on the bottom? One kilogram. And on the top? 1,000 grams. Remember, the units are also important, so keep that in mind. So when we do that, that cancels out kilograms. Is everybody OK with that? We're going to grams per cubic centimeter. So now we have units of grams. So we can stop with our master, stop converting. Is everybody OK with what I've just done? OK, so now we want to convert liters into cubic centimeters. But we don't have a direct conversion from liters to cubic centimeters, so we're going to have to convert liters to milliliters first. Is everybody cool with that? So we're going to use this metric to metric conversion that we've all memorized, right? One liter at the top, so we can cancel that out. And 1,000 milliliters at the bottom. So cancel, cancel. And that's grams per mill, right? Even though it would be the same number, it's not the same units. So we're going to do one more unit conversion. We're going to put what on top? One milliliter, very good. And one cubic centimeter on the bottom. Cancel and cancel. And notice our units now are in grams per cubic centimeter. Is everybody OK? So now all it is is a plug-and-chug problem, right? So really it's the same thing, right? So 12.88 divided by 4.77. Multiply by 1,000 divided by 1,000. So those cancel out, too. So 12.88 divided by 4.77. And how many sig figs is our answer going to have? Three, very good. 2.70 grams per cubic centimeter. So that's the density of the engine volume, OK? Any questions on that one?