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## 4. klasa

### Kurs: 4. klasa>Rozdział 14

Lekcja 7: Zamiana jednostek długości

# Przekształcenie jardów na cale

Dowiedz się jak zamieniać między sobą jardy, stopy i cale. Stworzone przez: Sal Khan i Monterey Institute for Technology and Education.

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## Transkrypcja filmu video

we're asked how many inches are in four and a half yards let me write that down four and one half yards now whenever we're dealing with fractions and we're going to multiply and divide by fractions it really complicates the issue to have a mixed number so right from the get-go I want to turn this into an improper fraction let me do it in over here in the top right four and a half written as an improper fraction is equal to what we're still going to have to as a denominator so 2 times 4 is 8 so 8 halves is the same thing as for right let me rewrite this this for just as a bit of a review for is the same thing as 8 over 2 that's the same thing as 4 and then you have that plus plus one-half that is going to give you nine halves the quick way to do it 2 times 4 is 8 8 plus 1 is 9 so 4 and a half is the same thing as 9 halves so four and a half yards is the same thing as we write it over here 9 / 29 / 2 yards now we want to convert this into inches now just so we can take this in baby steps maybe we convert this into feet first and then once we have it in feet then we can convert it into inches so to convert it into feet we just have to remember that there are three feet for every 1 yard so let me write that down there are there are three feet there are three feet per yard and if we were to multiply 9 halves yards times 3 feet this yard would be in the numerator and B divided by this yard and they would cancel out and we just be left with feet so we know we have to multiply by 3 you could say this is 3 feet for every 1 yard if it makes it simpler just 3 feet per yard and another way to think about it is however many yards you have you're going to have more feet right there are three feet per yard so if I have one yard I'm gonna have three feet if I'm gonna have two yards I'm gonna have six feet so you should think about in your head okay well yeah multiplying by 3 so that also makes sense so if we multiply by 3 right over here the nine times three is 27 / 2 over 2 times let me write it out let me take it step by step not skipping any step so this is equal to 9 over 2 times 3 over 1 times 3 over 1 yards this yards right here I'll do it an orange yards times feet / yards feet per yard times in this purple feet per yard the yards cancel out and you are left with nine times 3 is equal to 27 27 / 2 27 / 2 feet so we figured out four and a half yards is 27 over two feet and that makes sense because we should have more feet than yards and actually this should be three times more so everything makes sense this 27 / 2 is 3 times 9 over 2 so now we have 27 / 2 feet feet and now we want to convert this to inches and we just have to remember their 12 inches per yard and we're going to want to multiply by 12 because however many inches we have however many feet we have we're gonna have 12 times as many inches if we have one foot we're gonna have 12 inches to feet 24 inches 27 / 2 feet we're going to multiply it by 12 to get the number of inches so this is going to be x 12 and we'll make sure the D dimensions work out 12 inches 12 inches per foot and the feed and the foot day this is just the plural and the singular of the same word it's the same dimension this will cancel out so this will be if we just rearrange the multiplication view it as everything is getting multiplied and when you just multiply a bunch of things order doesn't matter so this is equal to 27 / 2 x 12 x 12 feet I'm just swapping the order feet x inches inches / feet or foot just the singular of the same word the feet and the foot cancel out there the same unit and you have 27 x 12 / 2 inches and what we could do here is that our final answer is going to be our final answer is going to be 27 x 12 over 2 inches and before we multiply the 27 x 12 and then divide by 2 you immediately see well i could just divide 12 x 2 + 2 x 2 and it makes our computation simpler 12 divided by two is six 2/2 is 1 so it becomes 27 x 6 inches and let's figure out what that is 27 27 x 6 7 times 6 is 42 2 times 6 is 12 plus 4 is 16 so it's equal to this is equal to 162 162 inches which makes sense four and a half yards that gets us to this number right here 27 divided by 2 is 13 and a half feet you multiply that by twelve it makes sense you can have a bunch of inches 162 inches