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Current time:0:00Total duration:6:22

Video transcript

throughout your mathematical life you will find situations where you will need to round numbers and you might be saying well what situations would that be well these would be situations where you're trying to get an estimate on things where you're trying to maybe you have a measurement and you're you want it to be a little bit less exact to simplify things or you don't trust how exact the measurement is so here we're going to actually think about what rounding is and we're going to round each of these numbers 36 34 35 26 and 12 we're going to round each of them to the nearest 10 and I'll give you a hint of that what that means that essentially says take each of these numbers and find the multiple of 10 that it is closest to so what are multiples of 10 well 10 times 0 0 10 times 1 is 10 20 30 40 50 60 so on and so forth so I encourage you to pause this video and just based on what I just told you what is the nearest multiple of 10 to each of these numbers try to think about that well to think about a little bit deeper let's actually put a number line here I'll put two number lines over here so we've got some number lines here and let's think about where these points would sit on this number line so this first number 36 where does it sit on this number line well it's between 30 and 40 and this little blue mark is 35 it's halfway between so 36 is going to be it's going to be a little higher than that so 36 is going to be right over here and if we zoom in between 30 and 40 so if we say that this is 30 and this is 40 where is 36 going to be so once again this is 35 36 is one notch above that so 36 36 is going to be right over here so if we're out if we want to round to the nearest 10 to the nearest multiple of 10 what are the two possibilities here well I could take 36 I could take 36 and I could round up to the multiple of 10 above it which is 40 so I could round up to 40 or I could round down to the multiple of 10 below it which is which is 30 and so I need to figure out which of these numbers is it closer to well when you just look at that even just blue eyeballing it you can see it but you could also say like 36 is only four away from 40 and it's six away from 30 it's closer to 40 so we are going to round up we are going to round up to 40 this is literally called rounding up now let's try some of these other numbers what about 34 and I encourage you to pause the video think about what number you would get if you were to try to round it up or round it down and then which one it is actually closer to well 34 is right over here on this number line 34 is right over there on this number line where we zoom in 34 is right over here 34 and we have two options the multiple of 10 above 34 let me do that those same colors the multiple of 10 above 34 is 40 multiple of 10 below 34 again is 30 now which one is it closer to what's only 4 away from 30 and 6 away from 40 so it's closer to 30 so we are going to round down to 30 we are going to round down to 30 and notice we went to 30 you might say hey when we rounded up the tens place increased from 3 to 4 from 30 to 40 maybe when we round down the tens place will decrease from 30 to 20 but no 30 is the multiple of 10 below 34 so when you round down you just go you keep the multiple of 10 but the ones place becomes zero now let's try a really interesting one let's think about rounding the number of the number 35 to the nearest 10 and first before we even try to do it let's think about the two options well we've already seen it 35 is sitting right over here on this number line that is 35 and once again we have two options 35 we can round it up to 40 or we could round it down to 30 I encourage you to pause the video and think about this well this one is a little bit of a conundrum because it's 5 away from both of them it's 5 away from 40 and 5 away from 30 so the mathematical community has decided to define what to do in the case where you have a 5 in the ones place if you have a 5 or more in the one's place you will round up this is just a rule five or more in the ones place you round up so thirty-five you round up to forty notice a six in the ones place was five or more so if you're rounding to the nearest ten you round up to forty a four in the ones place is not five or greater so we rounded down and so this gives a pretty good clue for these other two numbers let's try let's see what happens with twenty six twenty six what are the two options what is the multiple of 10 above twenty-six and what is the multiple of 10 below 26 well the multiple of 10 above 26 is 30 and the multiple of 10 below 26 is 20 so if we round up we go to 30 if we round down we go to 20 well if we're rounding to the nearest 10 we look at the tens place that's what we're going to round we're going to round to the nearest 10 but then we look at the ones place the ones place is going to decide it and we see here this is 5 5 or greater or you could say this is greater than or equal to 5 so we round up 26 rounded to the nearest 10 we round up to 30 now what about 12 what about 12 I think you're getting the hang of this well let's think about the multiple of 10 above 12 so we could either round up to 20 so 12 is sitting right around right around here we either round up to 20 or we round down to 10 well if we're going to round to the nearest 10 we have to look at the ones place we have to look at the ones place right over here this is less than 5 since it's less than 5 we round down which makes sense because it's also closer to 10 than it is to 20 so we round down and rounding 12 to the nearest 10 you actually get 10