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Current time:0:00Total duration:4:22

Rounding decimals on the number line

CCSS.Math:

Video transcript

so we are asked to drag the point to 12.5 on the number line so let's see you can see this is twelve and then twelve point five is halfway between twelve and thirteen then they say what is twelve point five rounded to the nearest tenth well what's cool about this is you can see on the number line that our tens are in this blue hash so we have ten and then 20 and we're between ten and twenty and which one are we closer to which is literally the nearest ten well you can see we're closer to 10 than we are to 20 so you would say ten and this helps us build an intuition for what rounding to the nearest 10 even means because you might know a rule like hey look you go one place less than the tens place which would be the ones place and if it's less than five there you round down to ten if it's five or greater you round up to 20 but you see why over here we are just closer to ten let's do another example here so here it says drag the point to zero point one three six so this is zero point one three this is zero point one four so this is 1300s and this is 1400s now let's see there's one two three four five six seven eight nine ten so these are you could think of it as the ten thousandth between these two hundredths so we want to go thirteen hundreds and then another six thousandths so let's see we go one two three four five six just like that and then they say what is this number 136 thousandths or 0.136 rounded to the nearest hundredth well we have our hundreds in blue here and which one are we closer to well we're closer to 1400s 0.14 and that's consistent with what we've seen in other cases where you look at the thousandths place and if it's five or greater you round up in this case you would round up to 14 hundredths let's do a few more examples here so let's say that so they're asking us which point is at forty four point one nine seven on the number line so let's see that's going to be between 44 and 45 so - right over here 44.1 97 so that would be point C and then they say what is forty four point one nine seven round rounded to the nearest whole number well there's a couple of ways to think about it you could just look at the tenths place and say look that's less than 5 so we round down to 44 or a more intuitive way of thinking about is like look Point C is the number we care about that is 44 point one nine seven is it close what's the closest whole number to it is the closer to 44 or is it closer to 45 well it's clearly closer to 44 and so that's another reason why 44 makes a lot of sense let's do let's do another example let's say that we want to so they say what is a rounded to the nearest thousandth what is a rounded to the nearest hundredth so a is right over here like let's get our bearings so zero point seven that seven hundredths this is eight hundredths right over here and then between them let's see this looks like it's zero this is so you could view this as seventy thousand seventy one thousand seventy two thousand seventy three thousand seventy four thousands and so on so this is between 78 thousands and seventy nine thousandths so if we round to the nearest thousandth it looks closer in fact it's definitely closer to seventy eight thousandths than it is to 79 thousandths so I would say this is zero point zero seven eight or 78 thousands it's closer that's the nearest thousandth what is a rounded to the nearest hundredth well what are the hundreds that it's in between it's in between seven hundredths and eight hundredths and which one is it closer to well it's closer to eight hundredths 0.08 so once again the whole point of this video is to appreciate when people say round to the nearest whole number to the nearest ten to the nearest thousandth to the nearest hundredth you can think of it on a number line and just say well what is the closest hundredth to it or what hundredth is it closest to which thousandth is it closest to on the number line