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Current time:0:00Total duration:2:37

Video transcript

what I want to do in this video is show you a way of subtracting numbers that is different than the regrouping technique and this is closer to what I actually do in my head and this might not be what you see in school so be careful while you're looking at this some people might not fully approve of what I'm about to show you but the idea the reason why I'm showing you this is to understand that there's not just one way to do things as long as you understand the underlying principles what these numbers represent and you do things that make sense you should be okay and what's neat about this technique because we don't have to regroup we're just going to start with the hundreds place and just keep on moving so for example if I think of 301 I first want to subtract 100 so 300 minus 100 is going to get me to 200 now I need to subtract 60 and so I can think about what is 20 to 0-6 so this is essentially was saying what is 200 minus 60 well 20 minus 6 is 14 so I just subtract and now I'm left with 14 and so now the problem has resulted in 141 minus 9 so I really just have to think about what well I could do what 141 minus 9 is well 141 it's a little bit more mental computation than you might be used to but 141 minus 9 is going to be 132 so we are left with 130 132 let's do this one same technique I encourage you to pause the video and try it yourself the same technique well 9 minus 2 is really 900 minus 200 you're going to be left with 700 then 71 minus 870 see 11 minus 8 is 13 so you're going to be left with you're going to be left with 63 and now we have to subtract 633 minus 6 13 minus 6 is 7 so it's going to be 627 627 and once again try to pause the video do it on your own so I don't have any hundreds to subtract so I can immediately go to 72 minus 8 which is really 720 minus 80 but let's just think in terms of 72 minus 8 well 12 minus 8 is 4 so 72 minus 8 is going to be is going to be 64 so now this is the same thing as 641 minus 8 well 41 minus 8 is going to be 33 you have to do a little bit of mental computation here so this will result in 633