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5th Grade Subtracting Mixed Numbers

Added Mar 15, 2017 •

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Check out this quick re-teach video on subtracting mixed numbers. You use the method that works for you :)

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types of graders it's misses Setter over the last few days we've been learning about how to subtract mixed now I taught you two different ways in class and I'm going to briefly go over that this evening in this video so that you can decide which method works better for you okay our first method is I'm going to rename the first fraction now we're dealing with mixed numbers remember that means a whole number and a fraction we're also going to be using some regrouping  okay the very first thing I'm going to do here is I'm only going to focus on my fractions I'm not even look at the whole numbers yet I will get to those in a minute okay I need to find a common denominator now I know you guys know how to do this cuz we've been doing this for a while now my common denominator the smallest one that I can use for six and eight is going to be 24  remember you could have 48 but then you'd have to do a lot more work at the end simplifying so it's easier to use the least common denominator okay we know how to get from here to to create an equivalent fraction  6 * 424 + 1 * 4 is 4 8 * 3 is 24 V * 3 is 15 now again I'm just looking at my fractions this is a subtraction problem  I think I might be able to do it because my denominators are the same but let's look at the numerators for take away five you can do that if you're going to talk about negative numbers but in this case we're not talking about negative numbers so I need to figure out how to make the for larger so that I can subtract 15 from it we're going back to old-school regrouping or borrowing I'm going to come way over what's my whole number 9 I'm going to cross out my 9 and it's going to become an 8 because I am going to borrow or regroup one hole I'm going to bring that one hole in front of my new fraction over here and imma make it kind of big on purpose so that you know what I'm doing added one whole  now this is a mixed number I'm going to convert this to an improper fraction 24 times is 24 + 4 is 28 my new fraction is 28 / 24 this fraction here did not change 15 / 24 can do this now my denominator is the same 24 that doesn't change 28 - 15 is 13 but I'm not done yet I've got to look at my whole numbers don't forget those 8 cuz I borrowed so it's no longer 9/8 take away 3 5  check and make sure you don't need to simplify at the end and we're good 5 and 13 over 24 is my so that's finding the answer renaming and regrouping just that first fraction okay when you have to regroup and borrow from your home so that's one method now I'm going to show you the next method this time same problem I am going to rename both numbers do that by changing these mixed numbers to improper fractions  6 * 9 is G4 plus one more is 55 and my denominator stays the same sing John here convert to an improper fraction 8 * 3 is 2424 + 5 is 29 okay so I have changed the entire fraction to an improper fraction I no longer have those whole number okay those whole numbers have been absorbed into my improper fraction okay so now I'm going to be doing some tracking okay well I can't do that because my denominators are not the same very similar to what we did in the very first problem that we did I need to find a common denominator my least common denominator is 24  so this is where it kind of gets a little tricky because you're going to be dealing with some numbers that are really big but some of these methods might work for you if it works for you that's fine you use what what makes sense to you okay six times for gets me 24 what * 55 is 220 again don't get freaked out of these big numbers  8 time 3 is 2429 * 3 is 87  okay now I'm going to be doing some subtracting I can do that now because I have denominators that are similar  220 - 87 is 133 in this not that you have to be a little careful there's a lot more room for error so you need to be kind of careful okay here is my answer and we know we cannot leave it like that that is an improper fraction never leave your answers in this form  can we all know how to change this we've been doing this for quite some time now I'm going to take my denominator and divide it into my numerator 24 x 5 that's as close as I'm going to get as you can see there's a lot more room for error using this method now my quotient my remainder and my dividend divisor are going to help me get my answer quotient is my whole number my remainder is going to be my numerator  and my the visor is going to be my denominator  this is my final answer 5 + 13 / 14 which just so happens to what's my answer here so I'm okay again you guys use what method works for you it doesn't matter to me again this one has a little bit more room for error what time do the little mixed up here too with the grouping into the whole numbers so again you guys use what works for you thanks a lot and have a good night bye

Uploaded by Kathy Seter.

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5th Grade Subtracting Mixed Numbers

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