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Lesson 2: Regroup whole numbers

# Regrouping whole numbers: 675

Sal regroups 675 into various addition problems. Created by Sal Khan.

## Want to join the conversation?

• I'm not understanding the concept of regrouping whole numbers in this video lecture. Are subtracting from these whole numbers to simplify the equation? I'm lost on this information. Crossing the numbers out and throwing lower numbers don't tell me anything. I throw my hands up in the air.
• So I think where people get confused on this is that they're trying to figure out WHY you would want to do this. Under normal circumstances, you probably wouldn't sit down and actually write all of this out. The idea here is that you can take a number and break it down into many different combinations of parts and still end up with the same total.

200 = 100 + 100
200 = 50 + 50 + 50 + 50
200 = 13 + 37 + 50 + 100

and so on...

You get the idea. It's just a basic concept.
• regrouing is important in math why?
• The concept is used as the basis for other things like borrowing and carrying.
• when i type my awser it says they understand but it is not right
(1 vote)
• is 45+45=50 67+4=71
(1 vote)
• its asking us to regroup 754,like the video
(1 vote)
• What if a zero is in the thousands place when you regroup your number?
(1 vote)
• It would be 0 thousands. For example 11527 would be 1 ten thousands + 1 thousands + 5 hundreds + 2 tens + 7 ones and could be regrouped to be 1 ten thousands + 0 thousands + 15 hundreds + 2 tens + 7 ones
(1 vote)
• I am now lost. Why are we giving a hundred a way? If you add 100s to the tens, doesn’t that mean you turn the 100s into thousands? Like, what’s the point of all this regrouping thing?
(1 vote)
• Can someone please clarify why I would ever want to regroup whole numbers? I do not think I have ever done so...
• Regrouping is needed in subtraction like 28-9=__ both the 8 and 9 is in the ones place but you cant take 9 from 8 so you regroup the 28 so the 2 would change to 1 and 8 into 18 so 18-9=9 and 10-00=10then just add to get the answer of 19
• How to round 234,489.0754 to the nearest thousand?
(1 vote)
• Thousand or thousandths? There is a huge difference between the two.
Once you know which place value you want to round to, find that place in your number. Let's say you want to round to the nearest hundredth in your number. That's the second decimal place and it has a 7 in it. Find the number just to the right of that number. In this case, it's a 5 so we will round up. 234,489.0754 rounded to the nearest hundredth is 234,489.08.
Rounding works the same with or without decimals. Look at the number just to the right of the place value you want to round to. That number will tell you if you should round up or round down.
• when its like 86 and they say round to the nearest hundred how do I do that