Calculating profit with multiplication

0:00- [Instructor] We're told that Sarah spent $79.98 on materials to create custom candles. She sold 12 candles for $14 each. What was Sarah's profit from the candle sales? So pause this video, have a go at that before we do this together. So let's just remind ourselves what profit is.

0:20Profit is going to be equal to the money that you earn. Maybe I'll write that in green 'cause that's a good thing, money that you earn, but you probably spent some money to get that money minus the money that you spent. So let's think about the money that Sarah earned here.

0:43Well, we see here that she sold 12 candles for $14 each. So the money that she earned is going to be 12 x $14. So there's several ways we could do that, but let's just do 12 x 14. We could say 4 x 12. Well, I'll just do it the standard way just to not confuse you a little bit.

1:054 x 2 is 8. 4 x 1. It's really 4 x 10 is 4 or 40. Since we're looking at the place values, we'll put a zero here since we're gonna be multiplying everything x this one now. And then 1 x 2 is 2 1 x 1 is 1. Or another way to think about that. 4 x 12 is 48 and 10 x 12 is 120.

1:26And now we can add all of this together. 8 + 0 is 8, 4 + 2 is 6. And then we have this one here. So the total money earned is $168. And what is the money spent? Well, it says that Sarah spent $79.98. So minus 79.98. If I figured this out, I know what the total profit is.

1:51Some of you might be able to do this in your head, but I will just break this down just to make this a little bit more straightforward. So we are going to have, lemme do that in green color, 168.00 minus 79.98. And what is this going to be equal to? Well, I'm gonna have to do a little bit of regrouping over here.

2:17And so I am going to, well even here, this eight is less than this nine. The six is less than the seven. So let's take this hundred and put it into the tens place. So it'd be 10 tens. So if we add those 10 tens to the six tens that are already there, we get 16 tens.

2:31And now I can take one of those 16 tens. So I have 15 tens and turn that into 10 ones. So now I have 18 ones, and then I can take one of those 18 ones. So now I have 17 ones and turn it into 10 tenths. And then I can take one of those 10 tenths. So now I have nine-tenths and turn it into 10 hundredths.

2:51And now I'm ready to subtract. 10 hundredths minus eight hundredths is two hundredths. Nine hundredths, sorry, nine tenths minus nine tenths is no tenths. And then 17 ones minus nine ones is eight. And then 15 tens minus 7 tens is going to be equal to 15 tens minus 7 tens is also going to be equal to eight.

3:19And so then we have, let's see, did I do all that right? Okay, there we go. We have $88.2. And I like to just double check that. If I were to subtracting $80, so if I just add 2 cents to this, if I were to subtract $80 from this, I would get straight to $88, but I'm subtracting 2 cents less than that.

3:41So it makes sense that I got to $88.2. Let's do another example. These are fun. So here we are told that Elena bought 15 vases for $12 each. She cleaned and polished the vases. Then she sold them for a total of $279.67. What was Elena's total profit from the vase sales?

4:02Again, pause the video, try to figure this out before we do this together. Well just remember, profit is money earned minus money sold. So what's the money earned? Well, that's what she sold them for. She sold them for a total of $279.67. $279.67. And from that we need to subtract the money spent.

4:24What's the money spent? Well, she bought 15 vases for $12 each. So let's multiply 15 x 12. 2 x 15 is 30, and then 10 x 15 is 150. We're going to get to 180. So you have $279.67 cents minus the total amount she spent, which is $180. And so this is going to be equal to.

4:51Some of you. I'll do it both ways. Well actually it gets a little complicated. So I'll just do the subtraction. So we're gonna have $279.67 minus $180. That's going to give us our total profit, Seven minus zero is seven. Six minus zero is six. Nine minus zero is nine.

5:14I could just think of 27 minus 18 is 9 and put that here. Or I could do a little bit of regrouping, take one of these hundredths and make that into 10 tens. So 17 minus 8 is 9 and then I have no hundredths left. So I get a total profit of $99.67. Another way that you could just make sure you're in the right ballpark.

5:36If this was $280, so just a little bit more minus $180, that would've been, that would've been $100. But we are just a little bit less, we're 33 cents less than that. And so it makes sense that we're 33 cents less than a $100 right over here.