Subtraction “Across the Zeros” 4th Grade Math Lightboard

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All right today we were going to work on subtraction mainly with working with zeros even the brightest students can have trouble sometimes with regrouping with zeros all right I want to show you four different examples this one I’ve
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just copied over here and this is going to be my example of what not to do I see some of my brightest students do this they’ll take this first number and they know they have to regroup and they make this a 14 to start with and then they
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say 14 minus 8 is 6 this is an absolute no-no and this is why if you do that you may forget that you need to borrow next-door so always borrow before you can spend it’s like going to the store you can’t spend money you don’t have
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so borrow first and then spend it watch this so here’s what to do you know you cannot take 8 from 4 so borrow next-door you cannot borrow from a 0 go to the next group over here borrow 1 from 7 is 6 now
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when you’re going across a 0 it always becomes a 9 technically you know it’s a 10 and then you borrow one and make it a 9 which is one less but anytime you go across a 0 just make it a 9 and save yourself a step now we have the 10 that
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now we can spend the money we can put the 10 on the 4 and it can become 14 this is the proper way in the proper order to be able to regroup do not do this you’ll forget and you’ll be sorry all right so here goes 14 minus 8 is 6 9
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minus 3 is 6 can you take 8 from 6 now we are going to have to borrow again do it right here then six with one less than six is five and ten more from six over on this column is 16 16 minus 8 is
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8 and 5 minus 5 is 0 so our final answer is 866 so you notice on the first example the thing to remember is when you go across a zero make it a nine let’s look at this example the zero is in a different spot let’s see if it
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makes a difference we’re going to take five away from zero you can’t go next door make it one less the 7 becomes six oh we’re not going across the zero we’re stopping at zero when you stop at zero it becomes a 10 every time now 10 minus
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5 is 5 move on to the next column can you take 9 from 6 no you can’t borrow next door this becomes one less which is a 2 now add 10 to the 1 right here this becomes 16 16 minus 9 is 7 go to the next column can you take 6 from – no you
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cannot borrow next door make the 4 one less add your 10 to the 2 which is 12 now 12 minus 6 is 6 and 3 minus 2 is 1 now the thing I want you to learn from this example is when you stop at 0 it becomes a 10 remember here when you go
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across it is a 9 let’s look at the next example the 0 is moving the 0 now is in a different spot it can be in any location let’s see what if this is going to be an example of going across or let’s see if it’s going to be one where
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we stopped 9 minus 6 take away a borrow the next door it becomes one less now the six is six plus 10 which is 16 16 minus 9 is 7 3 minus 3 is 0 moving right along 6 can you take 6 from 0 no you cannot
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make the 8 a 7 this becomes 10 more now we’re stopping at the zero we’re not going across to borrow for another column are we so this would be a case of stopping at the 0 right so stop at the zero it becomes a 10 10 minus 6 is 4 7
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minus 7 is 0 I bet you’re getting the hang of it let’s look at this next example here are a lot of zeros for can you take 4 from zero no can you borrow no can you borrow no you have to go all the way over to the thousands column to
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borrow benign becomes one less it becomes an 8 now here’s the fun part we’re going across the zero right this one becomes a you got it 9 we’re going across another zero what is it now yes it’s still a 9 now we’re stopping at
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this zero it’s going to be a 10 yes 10 minus 4 is 6 9 minus 2 is 7 9 minus 6 is 3 and 8 minus 5 is 3 if you will remember going across make it a 9 stop at 10 or 2 stop at the zero and it makes it a 10 all right it will help you with