Multi-step unit conversion examples (U.S. Customary)

- [Instructor] Brooklyn purchased three pounds of pasta and 12 ounces of cheese to make macaroni and cheese. What is the total weight, in ounces, total weight in ounces, of the pasta and cheese combined? So they give us the weight of the pasta in pounds, and they give us the weight of the cheese in ounces, and we want to add the total weight, but they have to all be in ounces. So let's first, let's first convert these three pounds of pasta into a certain amount of ounces of ounce, of pasta. So we already know that one pound is equal to 16 ounces. They tell us that. So what would three pounds be? So, if I had three pounds, how many ounces would that be? I encourage you to pause the video and think about it. Well, let's see, if you're having three times the pounds, you're also going to have three times the ounces. So, if one pound is 16 ounces, if you have three times as many pounds, you're gonna have three times as many ounces. So 16 times three is 48, 48 ounces. So Brooklyn, the three pounds of pasta that she purchased, that can also be viewed as 48 ounces. 48 ounces of pasta. So she has 48 ounces of pasta, and 12 ounces of cheese. So what is the total weight, in ounces, of them combined? Well it's going to be 48 ounces 48 ounces plus the 12 ounces of cheese. 48 ounces of pasta plus 12 ounces of cheese, give us a total of 60 ounces of pasta and cheese, combined. Let's do another example, with other units. So we are told, David is making a wall out of bricks. Each brick is 2/3 of a foot long. Each brick is 2/3 of a foot long. There are 20 bricks lined up end to end to make the wall. What is the total length of the wall in inches? We've got to pay attention to the units. So they give us the length of each brick in feet. So, we know that each brick here, let me draw a brick. The length here is 2/3 of a foot. 2/3 of a foot. So what would this length be in inches? Well, once again, we can look at the conversion between foot and inches. If I go from one foot to 2/3 of a foot, well I've multiplied by 2/3. So, if one foot is 12 inches, and if I want to know how many inches 2/3 inches, or 2/3 of a foot is in inches, well, I would multiply by 2/3 again. In either case, you could view this as multiplying both sides of this conversion, by 2/3. And so, 2/3 of a foot is 2/3 times 12 inches. And so 12 times two over three, that would be 24 over three. So this is going to be equal to 24 over three inches. I'll just write I-N for short, right over here. 24 over three, which is equal to eight inches. So each brick is, either you could view it as 2/3 of a foot long or you could view it as eight inches. Eight inches long. And there are 20 bricks lined up end to end to make the wall. So what is the total length of the wall in inches? Well, it's going to be eight brick, each brick is eight inches, times 20. Times 20. And eight times two is 16, so eight times 20 is 160 inches. Let's do one more of these. And this time, let's deal with some volume. So this says, Blanca buys two gallons of green paint. She uses five quarts to paint her front porch and 0.5 quarts to paint the front porch swing. How may quarts of paint does Blanca have left? So we're given the original amount in gallons, but we want to know how many quarts she has left. So let's convert the amount she originally has into quarts. So they tell us one gallon is equal to four quarts. So two gallons, two gallons is going to be equal to two gallons is going to be twice as many quarts, is gonna be eight quarts. So that's what she starts with. And one way to think about this, I just took this conversion, well if I'm a have twice as many gallons, then I'm gonna have twice as many quarts, if I want to express that volume in quarts. So, one way of thinking about it, she starts with eight quarts. She starts with eight quarts. Eight quarts. She uses five quarts to paint her front porch. So minus five quarts, on the front porch, is what she used. And she used .5 quarts to paint the porch swing. So minus 0.5 quarts. That looks like a "g." 0.5 quarts. Well, what is that going to be? Well, eight minus five is three, minus .5 is 2.5. So she is going to be left with 2.5 quarts. And we have answered the question in terms of the units they care about. In terms of quarts.