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Current time:0:00Total duration:3:36

Video transcript

what I want to calculate in this video is 53 plus 17 plus 17 and the way that I want to do it is by breaking up the 53 and then rearranging the numbers and you'll see what I'm talking about in a second so 53 plus 17 that's going to be the same thing as well I'm going to break up 53 essentially into the tens and the ones so 53 can be rewritten as 50 50 plus 3 that's 53 right and I could put parentheses around it like this so these curvy things so this is an open parenthesis and this is a closed parenthesis this just means to do what's inside the parenthesis first so 53 is the same thing as 50 plus 3 and we still have the plus we still have the plus 17 now I could I could just add the 50 plus 3 first and then add the 17 and I would just get back there but we want to figure out what this whole thing is so I could rewrite this I could rewrite this this is the same thing as 50 plus 3 plus 17 plus 17 and I could do the 3 plus 17 first so here I'm doing the 50 plus 3 first I have those in the parentheses here I have that I'm doing the 3 plus 17 first and this is just a property of addition that I could do this I could change the order in which I'm adding so here I'm adding 50 plus 3 first here I'm going to add 3 plus 17 first and so what's this going to be equal to well this is going to be equal to I have my 50 here I have my 50 plus now what's 3 plus 17 what's 3 plus 17 well 3 plus 7 would be 10 so 3 plus 17 is going to be 20 so it's going to be 50 plus 20 now what's that going to be well it's five tens plus two tens which is going to be equal to this is just going to be equal to seven tens or seventy let's do another example and this is going to be one like the type of exercise that you might see on Khan Academy so let's let me take open that up so they'll say complete to solve for t1 plus nine so once again we can look at four we can look at we can look at the 41 we could break it up 41 is the same thing as 40 plus what well it's 40 plus one and of course then you have the plus nine there and I can do the nine see this plus nine is this plus nine there now they change the order in which we're adding so 40 plus one that's in the parentheses and then you add nine well that's the same thing as 40 plus well that's the same thing as 40 plus one plus nine so here we're doing the one plus nine first and if we do the one plus nine first what do we get well one plus nine one plus nine is what well that's just going to be equal to ten notice what's this this box is replacing what was in the parenthesis before so in front in the parenthesis you had one plus nine well that's 10 and what's 40 plus 10 well it's four tens plus 110 so that's five ten or 50 and we're done