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Current time:0:00Total duration:3:45

Video transcript

we've got six thousand seven hundred ninety eight minus three thousand three hundred and fifty nine so let's see how far we can get with the subtraction so immediately when we go into the ones place we're going to try to subtract a 9 from an eight so we read it immediately reach a little bit of a stumbling block and to see what our options are here in terms of regrouping I'm going to rewrite both of these numbers so I'm going to rewrite six thousand seven hundred ninety-eight literally so this is equal to six thousand that's this right over here that's six thousand plus 700 plus seven hundred plus 90 plus 90 plus eight I do plus eight plus eight minus all of this so - so I could do it I could subtract each of the places so I could say this is going to be minus three thousand so minus three thousand - 300 - 300 - fifty - fifty if five and a tens place is just fifty minus nine minus minus nine so they are here we're just explicitly showing what those place values represent a six in the thousands place is six thousand a three in the hundreds place is three hundred let's go back to our problem we wanted to subtract a 9 from an eight well that's a little bit of a stumbling block but what if we could take some of the value from some of these and give it to the eight in particular we could go one place value up to the 90 and what if we were to take 10 from the 90 so let's do that if we were to take 10 from the 90 the 90 because 80 but we don't want to change the value of the entire number so we're going to give that 10 to this 8 so we're going to give so we gave we're going to give that 10 to the 8 we're essentially regrouping right over here and send that 8 can become an 18 notice I did not change the value of the number I just essentially changed how I represented it instead of saying it's 6,000 plus 700 plus 90 plus 8 I'm just saying that it's 6,000 plus 700 plus 80 plus 18 those are both going to give you 6 thousand seven hundred and ninety eight but now it becomes a little bit easier for us to actually subtract now if we subtract now if we subtract I have 18 minus 9 which is 9 I have 80 not 90 now I have 80 minus 50 which is 80 minus 50 which is 30 and these are all positive so this is plus 9 this is a positive 30 80 minus 50 is 30 I have 700 minus 300 which is 400 and I have 6000 - 3000 which is 3000 3000 so this is literally going to be 3000 plus 400 plus 30 plus 9 or 3439 now how would you do it if you didn't want to write it out like this and this is where you'll see kind of a shorthand notation this is often called borrowing so you say look I got an eight in the ones place I want to take a 10 from this 90 so it's going to become it's going to become an 80 but we'll just write it as an 8 because it's in the tens place this 8 represents the 80 and I'm going to give that 10 to the ones place so 10 plus 8 is 10 plus 8 is 18 and now you can subtract 18 minus 9 is 9 8 minus 5 is 3 7 minus 3 is 4 6 minus 3 is 3 3439