So when we're dealing with any type of question or trying to write down the answer to a question, we need to take into account significant figures. Significant figures are the numbers that contribute to the precision associated with any value. We're going to say here that there is an easy way and, of course, a hard way to approach significant figures. Luckily for us, we're going to focus on the easy way. The hard way has a lot of rules and it has terms that sometimes might be confusing, such as leading zeros and trailing zeros. We're going to avoid all of that, and we're going to rely on 3 simple rules to help us determine the number of significant figures associated with any value.

Now the first rule is, if your number has a decimal point, you're going to move from left to right. Start counting once you get to your first non-zero number, and keep counting until the end. Here we have our first two examples. One is written in standard notation. One is written in scientific notation, but that doesn't matter. If we look at the first one, we're moving from left to right. We're going to start counting once we get to our first non-zero number. So 0, 0, 0, 0, here's our first non-zero number, this 2. We're going to start counting there, and we count all the way until the end. So 1, 2, 3. This number has 3 significant figures. For the next one, it's written in scientific notation, but that doesn't matter. When it's written in scientific notation, focus on the coefficient, this part here. The base, which is the 10, and the power, the exponent, don't matter. It has a decimal point, so we're moving from left to right. Our first non-zero number is this 8. We start counting there, and we count all the way until the end. So 1, 2, 3. So we have 3 significant figures in this one as well.

Next, if your number has no decimal point, then we're going to move from right to left. The same rules apply. Start counting once you get to your first non-zero number and keep counting until you get to the end. Our first non-zero number is this 5. So that's 1, 2, 3, 4. So we have 4 significant figures here as our number of significant figures.

Now, this third rule is a little bit different. This rule deals with exact numbers. An exact number is a value or integer, meaning it has to be a whole number, that is known with complete certainty. We're going to say here, for an exact number, there are an infinite number of significant figures. For example, your lecture class has 125 students. That's something we can know with certainty, because we can literally count the number of students that we see within the room. Or a dozen eggs equals 12 eggs. This is something that is known with complete certainty. 12 eggs. We can count each one of those individual eggs. So 125 students within a lecture hall has an infinite number of significant figures. 12 eggs equal 1 dozen. That can also have an infinite number of significant figures. That's because, for example, if we're looking at the 125 students, it could be 125, which would have 3 significant figures, or it could be 125.0, that's still saying 125, that has 4 significant figures, or it could be 125.00, which has 5 significant figures, and it can go on and on because technically that is still saying 125. So just remember, the first two rules are pretty simple. That deals with decimal place or no decimal place. The third rule is a little trickier. You have to recall that this is an exact number, something that can be counted, that you can know for certain, 100%, that it's that number. Those have an infinite number of significant figures.

Now that we've taken a look at these three rules, let's move on to the example question in the following video and see if we can determine the number of correct significant figures.