Calculating profit with addition and subtraction

0:00- [Instructor] We're told that Lily bought a backpack for $26.45 and spent $18.97 on accessories to decorate it. She sold the decorated backpack for $67.56. What was Lily's total profit from selling the custom backpack? All right, pause this video and have a go at that before we do this together.

0:25Okay, well let's just first think about what profit is. So profit, you can view it as money earned. Money earned. Minus money spent. Minus money spent is going to be equal to your profit. Lemme do this in another color. So this is going to be equal to your profit.

0:50So what you need to do is just figure out what's the money earned and then what's the money spent and then subtract them. So what's the money earned? How much did she bring in? Well, the money earned in this situation is going to be what she sold the backpack for.

1:05That's what she got. So the money earned is this piece right over here, $67.56. That's the money earned. So we have $67.56, and then we're going to subtract from that the money spent. Now what was the money spent? Well, she spent some money twice. She bought a backpack for $26.45 and then she spent another $18.97 on accessories to decorate it.

1:32So the total money spent, I'll do it over here. Money spent. The total, maybe I'll just write it here. Let me just write it. So money spent. Money spent is equal to $26.45. Actually, let me do it over here 'cause actually I just wanna line them up so I can just do the computation.

1:55So it's $26.45 plus $18.97. Let's add these together. We'll go to the pennies or the hundredths place. Five plus seven is 12. Write the two there, regroup that one. And now we have one plus four plus nine is going to get us to 14. We could put the four there. Regroup that one, that's a whole.

2:17Put the decimal there. One plus six plus eight, that's seven plus eight, which is 15. Regroup the one. One plus two plus one is 45 or actually it's 40 or four. And so this is $45.42 is what she spent. So money earned, that's what she brought in minus what's spent is $45.42.

2:37And so now we just have to do this subtraction to get our profit. And actually let me do that over here. So if I have 60, that's too light of a color. If I have $67.56. And from that I am subtracting $45.42. So let's see if I have six minus, I'll put the decimal here.

2:59Six minus two is going to be four. Five minus four is one, seven minus five is two, six minus four is two. So we get to $22.14 of profit. Let's do one more example here. So lemme delete this. And now let me bring up another problem and move it up so we can see it properly.

3:28And so here we are told that Maya spent $9.24 on ingredients to bake two cakes. She sold one cake for $13.29 and the other for $17.45. What was the total profit from selling the two cakes? Again, you could pause this video, have a go with that. Well, once again, it's money earned versus minus money spent.

3:49So what's the money earned? So the money earned here is, so this is how much she spent and then, but what she sold it for, that's the money that she got. So she sold one cake for $13.29 and the other for $17.45. So let's see if we add the both of these, that's her total money earned.

4:11So nine plus five is 14. One plus two plus four is seven. Three plus seven is 10, regroup that one. One plus one plus one is three. So total money earned is $30.74. And from that we're going to subtract the money spent, minus $9.24. Lemme do that in another color.

4:32So minus $9.24, which is that right over there. And we could do this separately, or you might be able to do this in your head because if you have 74 cents minus 24 cents, that's going to give you 50 cents. And then $30 minus $9 is $21, is $21.50. You could also write it out the way we did the last one where you just put the 9.24, line up the decimals and subtract accordingly.

5:00But that's her total profit from selling the two cakes. And we're done.