 Let's do a video this morning on Exact and inexact numbers. So you can see here. Hopefully we've got four beakers filled with water and I'm so four different size beakers and we're going to See actually the difference between exact and inexact numbers. So an Exact number in this situation would be four as if we're talking about the beakers. So There is exactly four one two three four It's unambiguous that number. All I have to do is count it. So there's no What do you say wiggle room? There's no uncertainty Okay, so let's look at some Inexact measurements with these same Objects so like I said they're partially filled with water. So you can see this is a 30 mil beaker and it's filled in between the graduations of five and 15 With water. So I have an uncertainty in that measurement. I'm not really certain exactly How many mils of water I have so I mean I can approximate I could say it's probably 10 mils of water But it might be 11. It might be nine. It might be 10 so I'm not sure it might be 10.2. It might be 10.23847 Okay, so there's an uncertainty associated with that measurement as opposed to the measurement That I said there are one two three four beakers exactly So let's do another uncertain number Okay, so let's look at this 150 okay, so the 150 has graduations 80 and 100 here. So the one in between I'm assuming is 90 So if we look at where the meniscus is of the water and in fact What you'll realize is beakers are very bad to use as measuring devices for volume. They get good approximate volumes but to measure a Exact number you're going to want to use either a graduated cylinder, which is more exact or a volumetric flask of course or graduated pipette for that matter Or a volumetric pipette, which is even the best so you can see here. This is going to be below 90 but above 80 so that's not very doesn't I mean way above 80, but a little bit below 90 So I mean I could approximate that is about 88, but again, that's an approximation So it's an inexact number. Okay, it's a number. It's a quantitative measurement So let's be make sure that we understand that both the exact number and these inexact numbers are both Quantitative measurements. So I'm quantitatively measuring one two three four Quantitative because there's a number associated with it and I'm quantitatively measuring 88 mils, right? But the 88 mils is an inexact number Whereas the four beakers is an exact number. Here's another one. We can do it again so we look 50 100 so that must be 75 that must be 125 so again, I Don't know maybe 120 118 Very very difficult to tell Okay, exactly, right? That's why it's an inexact measurement And again, we can do the same thing here So what do we got it's right below? 600 if you guys can see that right below 600 so maybe I'd measure that at I Don't know 690. I can definitely say exactly. There's one 1,000 mil beaker Okay, and exactly There's one 250 mil beaker and exactly there's one 150 and exactly 130 beaker But I can't say exactly how much those beakers contain Of water inside of them. So hopefully this helps you understand exact and inexact numbers