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Үндсэн товъёог
Цаг: 0:00Нийт үргэлжлэх хугацаа:4:49

Video transcript

let's get some practice subtracting mixed numbers so let's say that I had two and 5/8 minus minus one and two eight minus one and two eighths what is this going to be and I encourage you to pause the video and try to work it out well we could rewrite this we could write the numbers on top of each other we could say this is to do that magenta color say this is two and five-eighths actually let me write them a little bit further spaced apart two and 5/8 minus minus one and two eighths and then we can subtract and we could say okay look in this column right over here we are subtracting eight we have five eighths and we're going to subtract two eighths if I have five of something and I subtract two of them I'm going to have three of that something and in this case we're talking about eighths so five eighths minus two eighths is going to be three eighths and then you have two ones minus one one or two minus one is going to be one so this is going to be equal to one and three eighths now let's do something more interesting let's say that we had three I'm just going to make up a number here three and two-fifths three and two fifths minus minus two and three fifths and like always pause the video and try to work it out let's try to work it out this exact same way so I'm going to rewrite it as three let me do that same magenta color trouble changing colors we have three and two over five minus -2 and 3 over 5 two and three over five and when you first try to do it over here you had five eighths minus two ways that was easy to figure out that's three eighths but then over here you have two fifths minus three-fifths well that's hard three fifths is larger than two-fifths so what can you do here well one option is to regroup let's take one from I guess you could say the ones place here so let's take one from this and then that's going to turn into two and then one is the same thing as 5/5 so 2 plus 5/5 is equal to seven fifths so another way of thinking about it I'll do it over here we could write we could write the same 3 and 2/5 is the same thing as two and seven fifths two and seven fifths these two things are equivalent why well I took one away from here to get to two and then I added that one over here one is the same thing as five fifths two fifths plus five is seven fifths so now if we consider this if we consider this thing to be two and seven fifths we're ready to subtract if you say seven fifths if you say seven fifths minus three-fifths that's going to be four fifths and then you have two minus two is zero one so you're just going to be left with four fifths so this is just going to be four fifths let's do that again let's do one where we have to regroup again and I'll just write it out in a column up down to begin with let's say that we have seven and seven and one six minus minus four and four and five six minus four and five six so what is this going to be equal to well when we try to subtract five six from one six well that's hard five six is larger than one six but we can regroup we could take one from here so the seven becomes a six and then we take that one which is the same thing as six sixths and add it to one six so 1/6 + 6 6 is going to be 7 6 is going to be 7 6 let me be clear what I did I took one from the 7 and it became 6 and 1 is equal to 1 is equal to 6 6 and so I added 6 6 to that one 6 and I got 7 6 so I took the 1 from here and I added it over here and the whole purpose is now 7 6 is greater than 5 6 so 7 6 - 5 6 is I'm doing that orange color is 2 6 and 6-4 6-4 is 2 so it's going to be 2 + 2 6 or if we wanted to rewrite 2 6 let's see they're both divisible by 2 this is the same thing as 2 and 1/3 is equivalent to 2 6 so you could also write it like that