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### 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``
• 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``
• I have two boys with special needs (FAS/FAE), one of which is having a difficult time understanding carrying over to the tens/hundreds. Your video does an excellent job for my other son and he understands the concept. Are there any other methods/techniques to introduce this concept of carrying over?
• You can always try a visual approach like with objects in the real world. When I was smaller I learned better with a visual that I could touch and interact with. Some examples of items you could use are candy, tokens, fruits (just things around the house, honestly). I hope this helps!
• Why can't you "carry the two"
• You can carry a 2. Lets say you were asked to add 19 + 9 + 39, while you are adding all the numbers in the ones column you would get 9 + 9 + 9 which equals 27. In this case you would write the seven and carry a 2 instead of a one over to the tens column. Now in the tens column you would add 2 + 1 + 3 which equals 6. Notice the 2 is from the 27 you carried over from the ones column. So your answer to 19 + 9 + 39 would be 67.
• Why do you use the expanded form when you can use subtraction to check?
• The teachers want you to know exactly how you found what you found and so you know how to do it if you have a bit of trouble, and this is third grade work...they want them to show it.
(1 vote)
• At it doesn't make sense
• if (x < 0) {
return;
}
• From to why do you put it in expanded form?
• The expanded form is what explains why carrying works.
Here's an example:

286 = 200 + 80 + 6
+148 = 100 + 40 + 8
-------
6+8 is 14 which is equal to 10 + 4. the unit digit is 4 we "carry" the 10.
now we have 10 + 40 + 80 = 130 which is equal to 100 + 30. 3 is the tens digit. We "carry" the 100.
and finally, 200 + 100 + 100 = 400, so the hundreds place has the digit 4