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## Arithmetic (all content)

### Course: Arithmetic (all content)>Unit 2

Lesson 16: Addition with regrouping within 1000

# Using place value to add 3-digit numbers: part 2

Learn to use regrouping to add 536+398. Created by Sal Khan.

## Want to join the conversation?

• Why is it that you can only "carry the one" and never "carry the two"?
• Good question. When you add two numbers, you are adding pairs of digits, as in the video. Those pairs can never add up to more than 18, (or 19 when you are carrying 1) .

But if you are adding three or more numbers, the digits you add together can add up to more than 18, in which case, you might have to carry two, three, or more.

Let' s try 276 + 499 + 387
276
+499
+387
-------
2 Two units
2 Carry two tens
62 Six tens and two units
2 Carry two hundreds
1162 One thousand, one hundred, six tens and two units
• why did Sal do it in expanded form?
• Sal was trying to show you why adding the numbers in each column and carrying the digit works. He wants you to understand that we aren't just adding single digit numbers. Instead, they have place value (units, tens, hundreds, etc)
• You can carry the two or any other number?
• Yes, it doesn't matter what the integer is, as long as it is of a greater place value that you are adding up, it should be carried over to the respective place value. For example:
18
28
15
9
+14
¨¨¨¨¨¨¨¨¨
84

When you add up the numbers in the ones place, you get 34. You then carry the thirty over to the tens place and represent it as a 3.
• What if you were adding in the ones place and you had to carry 100
(Or a 1000 in the situation of the ten's place, and so on)?
• my bro this is because 9 is a single digit number so there is no need of carrying.
• I do not get it
• In life, is there math involved?
• Yes. For example, if you go out to a store to buy a product, you will calculate the cost of what you have and what you will pay. Math comes in handy by helping you calculate not just costs of what you have and what you will pay, but will also calculate what you will need for taxes, fees, and maybe even warranty (depending on what product you get).
• you can only carry two when you have a twenty something
• It is not possible to end up with a twenty something when adding only two numbers together. So your (correct) statement means that in order to carry two, you have to be adding more than two numbers together.

Have a blessed, wonderful day!
• how many three-digit numbers have three different digits?
• The answer is 648. There are several ways to arrive at this.
• What if you were adding in the ones place and you had to carry 100
(Or a 1000 in the situation of the ten's place, and so on)?
• This might be an example of the situation that you're asking about.
+9.9999
+0.0003
-------
?

To add these two decimals, the 3+9 = 12. Write a 2 in the ten thousandths' place. Carry the 1.
Then 9+0+1 = 10. Write a 0 in the thousandths' place. Carry the 1.
Then 9+0+1 = 10. Write a 0 in the hundredths' place. Carry the 1.
Then 9+0+1 = 10. Write a 0 in the tenths' place. Carry the 1.
Then 9+0+1 = 10. Write a 0 in the units' place and a 1 in the tens' place.

Final answer after all that carrying:
+9.9999
+0.0003
-------
10.0002