 Okay, let's do this problem as our first significant figure problem. So I guess the question to this asks, put the answer into the correct number of significant figures. So let's first just go ahead and plug all this stuff into our calculator and see what answer we come up with, okay, and see what the calculator says. So 4.2 times 10 to the third, remember we just learned or you're about to learn that this is written in scientific notation, this number, so this is all one number, actually. And there's only two significant figures that come from just this 4.2. This is not considered significant, okay, so whenever you see a number in scientific notation it's just these numbers that are significant. So 4.2 E3 times 15.94, so how many does this have? So this has two, this number here has four, okay, and then divide that number by 2.255 E negative 4. Why? Because it's again in scientific notation here. So how many numbers does this have? How many sig figs does this have? Four is what? One, two, three, four. Why? Because these are not considered significant. So when we divide that, we get this number. So 2, 9, 6, 8, 8, 6, 9, 1, 7, 0.96. So if you put that, I guarantee you're going to get that probably marked wrong in some sort of fashion. Why? Because it's got way too many significant figures. So you're actually saying that this number is exactly all the way up. It's exactly this number all the way up to here. But you can't say that. Why? Because you've got these three numbers that you've used, these three measurements that you've used to come up with this other number that have much fewer significant digits than what you're giving back. So what you're saying is this is much more precise than the measurements that I've taken. So obviously that can't be the case. So you've got to do something about that. So in other words, what we need to do is figure out how many significant digits can this number go to. So how do we figure that out? Well we look at how many significant digits these numbers were at and we already figured that out, so two, four, and four. So we can only report our answer to the least number of significant digits. So that's two. So that's just these two numbers there. And of course we're going to round up because of that number. So anyways, when we do that, we're going to have to report our final value with only those two numbers or those three numbers in mind, reporting only those two numbers. So we're going to report it as two significant digits. So three, zero, why? Because we're rounding that nine up from a six because the six is higher than five. And we're going to put this into scientific notation actually because all of these numbers we can't account for. So we'll put a decimal point there and then we're going to move this decimal point. One, two, three, four, five, six, seven, eight spots like that. Three point zero times ten to the eighth is our number. To the correct number of significant digits, why? Because you reported it to two, right? And your least number is two. This one was reported to one, two, three, four, five, six. We can obviously do that unless you're the least one over here. What's the left? Okay, so hopefully that's a good start to the day I think.