Decimal Multiplying Rules

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When multiplying decimals, it is always important to keep a few rules in mind. Learn about decimal multiplying rules with help from a mathematics educator in this free video clip.

Part of the Video Series: Mathematics Equations & More
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Video Transcript

Hi, I'm Jimmy Chang and we're here to talk about decimal multiplying rules. Now, when you multiply decimals together it actually works the same way as traditional long multiplication. The only thing you got to keep in mind is the decimal places of the numbers themselves and as we do an example you'll see how this works. So let's look at an illustration that we have with two decimals, lets just say you have two-point-three times lets just say four-point-one. Now, treat this as a standard multiplication problem and worry about the decimals later which we'll get to towards the end of the problem here. So you start by multiplying the one through all of these numbers so one times three is going to give you three, one times two is going to give you two. Now, as you know when you multiply the second number, you multiply the four, you have to allow a little bit of you know one space over before you start multiplying, just one of those standard multiplication rules. So you have four times three that's going to give you twelve, remember you got to carry over the one here so four times two is going to give you eight, add the one's going to give you nine and then you're ready to add. Now, what you want to do is treat this you know as you normally would with standard multiplication so you got three here, you have two, two plus two that's going to give you four and of course you have nine, now you get to the decimals. What you want to think about here is how many decimal places are in each number and then what you want to do is you want to add the number of decimal places that you have. So for example, two-point-three has one decimal place, four-point-one has another decimal place, you want to add those two together so one decimal place plus another one decimal place that's going to give you two decimal places. So hypothetically, if this second number had another decimal place you would have had three, but for all intensive purposes of this particular problem there's two decimal places. So what you got to think about is take the nine, four, three and then take your decimal and move it twice and establish your decimal here. So that means you're final answer's going to be nine-point-four, three. So in terms of multiplying decimals, decimal multiplying rules, you just got to think about how many decimal places do have for each problem and then add all the decimal places together. So I'm Jimmy Chang and that's a demonstration on decimal multiplying rules.


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