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CCSS.Math:

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 amount 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 add three pounds how many ounces would that be and encourage you to pause the video and think about it 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 3 is 48 48 ounces so Brooklyn the 3 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 twelve 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 have 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 two-thirds 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 going to be 2/3 times 12 inches and so 12 times 2 over 3 that would be 24 over 3 so this is going to be equal to 24 over 3 inches I'll just write in4 short right over here 24 4 3 which is equal to 8 inches so each brick is either you can either view it as 2/3 of a foot long or you could view it as 8 inches 8 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 it's going to be 8 brick each brick is 8 inches times 20 times 20 and 8 times 2 is 16 so 8 times 20 is 160 inches let's do one more of these at this time let's deal with some volume so this is 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 many quarts of paint does Blanca have left so we're given the original Mountain gallons but we want to know how many quarts she has left let's convert the amount she originally has into quarts so we they tell us 1 gallon is equal to 4 quarts so two gallons two gallons is going to be equal to two gallons is going to be twice as many quarts is going to 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 gonna have twice as many gallons then I'm going to have twice as many quarts if I want to express that volume in quarts so one way of thinking about she starts with eight quarts she starts with eight quarts eight quarts she uses five quarts to plate to paint her front porch so minus five quarts on the front porch is what she used and to use 0.5 cores to paint the porch swing so minus 0.5 quarts that looks like a G zero point five quarts well what is that going to be well 8 minus 5 is 3 minus 0.5 is 2.5 so she is going to be left with two point five quarts and we have answered the question in terms of the units they care about in terms of quarts