Rounding whole numbers
Rounding Whole Numbers 1 Rounding Whole Numbers 1
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- Round 24,259 to the nearest hundred.
- You're going to find that doing these problems are
- pretty straightforward, but what I want to do is just
- think about what it means to round to the nearest hundred.
- So what I'm going to do is I'm going to draw a number line.
- Let me draw a number line here, and I'm just going to
- mark off the hundreds on the number line.
- So maybe we have 24,100, and then we go to 24,200, then we
- go to 24,300, and then we go to 24,400.
- I think you see what I mean when I'm only
- marking off the hundreds.
- I'm going up by increments of 100.
- Now, on this number line, where is 24,259?
- So if we look at the number line, it's more than 24,200
- and it's less than 24,300.
- And it's 259, so if this distance right here is 100, 59
- is right about there, so that is where our number is.
- That is 24,259.
- So when someone asks you to round to the nearest hundred,
- they're literally saying round to one of these increments of
- 100 or round to whichever increment of 100 that it is
- closest to.
- And if you look at it right like this, if you just eyeball
- it, you'll actually see that it is closer to 24,300 than it
- is to 24,200.
- So when you round it, you round to 24,300.
- So if you round to the nearest hundred, the answer
- literally is 24,300.
- Now that's kind of the conceptual understanding of
- why it's even called the nearest hundred.
- The nearest hundred is 24,300.
- But every time you do a problem like this, you don't
- have to draw a number line and go through this whole process,
- although you might want to think about it.
- An easier process, or maybe a more mechanical process, is
- you literally look at the number 24,259.
- We want to round to the nearest hundred, so you look
- at the hundreds place.
- This is the hundreds place right here, and when we round,
- that means we don't want any digits.
- We only want zeroes after the hundreds place.
- So what you do is you look at the place one less than the
- place you're rounding to.
- This is the hundreds place so you look at the 5 right there,
- and if this number is 5 or greater, if it's 5, 6, 7, 8,
- or 9, you round up.
- So 5 or greater, you round up.
- And so rounding up in this situation, it is 5.
- It is 5 or greater, so rounding up means that we go
- to 24,000, and since we're rounding up, we make
- the 2 into a 3.
- We increment it by one, so rounding up, so 24,300.
- That's what we mean by rounding up.
- And just as kind of a counterexample, if I had
- 24,249 and I wanted to round to the nearest hundred, I
- would say, OK, I want to round to the nearest hundred.
- Let me look at the tens place, this place one
- level to the right.
- It is not 5 or greater, so I will round down.
- And when you round down, be careful.
- It doesn't mean you decreases this 2.
- It literally means you just only have the 2.
- Just get rid of everything after it.
- So it becomes 24,200.
- That's the process where you round down.
- If you round up, it becomes 24,300.
- And it makes sense.
- 24,249 is going to be sitting right over here someplace, so
- it's going to be closer to 24,200.
- 24,200 would be the nearest hundred when we round
- down in this case.
- For the case of the problem, 24,259, the
- nearest hundred is 24,300.
- We round up.
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