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### Unit 1: Lesson 5

Topic E: Multi-digit whole number subtraction

# Multi-digit subtraction with regrouping twice

Sal using regrouping to subtact 9601-8023. Created by Sal Khan.

## Want to join the conversation?

• Can you put the bigger number on top or not?
• yes you can because in addition and multiplication it doesn't matter if the larger number is on top or bottom.

Ex.
4169 8234
+ +
8234 4169

because they both equal 12403 anyway
• 128-100=-28 Is that correct
• (1.) 128 - 100 = 28 (The smaller number subtracted from the larger)
(2.) 100 - 128 = (-)28 (The larger number subtracted from the smaller)
• I can see but it would be quicker if you put it vertically and added digit by diget
(1 vote)
• what about 1332-1546 Doesn't sound easy but you can just use a calculator if you need help but anyways here is the answer. -214 which is negative 214 you welcome
• 1546 is greater than 1332, so (1332 − 1546) is going to be a negative number.

The trick is to factor out (−1):
1332 − 1546 = −(1546 − 1332)

1546 − 1332 = 214, so 1332 − 1546 = −214
• thank you sal you tot me a ting or two
• what if you get to a problem that you can't do and you try regrouping it but it doesn't work
• it has to work if you regroup you will get the anwser unless you regrouped wrong
(1 vote)
• rly would like to see the expanded solution of 2000 - 105 as example for 4th grade

2000 + 0 + 0 + 0
.......... - 100 - 0 - 5

(regrouping 1)
1000 + 1000 + 0 + 0
........... - 100 - 0 - 5

(regrouping 2)
1000 + 900 + 100 + 0
........... - 100 - 0 - 5

(regrouping 3)
1000 + 900 + 90 + 10
........... - 100 - 0 - 5
= 1000 + 800 + 90 + 5
• try subtracting 1232-2576 I will put the answer anyways so you don't have to look it up -1344 same as the last question/answer it is negative 1344 you welcome.

(1.) Expanded the top number becomes 1000 + 200 + 300 + 20
(2.) Expanded the bottom number becomes 2000 + 500 + 70 + 6
(3.) The regrouping shown in the video can't be done easily for this problem; however, you can switch the place of the minuend (1,232) with the subtrahend (2576).

2576 - 1232

Once that has been done, you can subtract normally. No major regrouping is needed. After you finish subtracting, be sure to place the negative sign (-) in front of the answer as 2,567 subtracted from 1,232 would produce a number with a value less than 0.
(1 vote)
• I still don't get how five hundred becomes ten. Could someone please explain? I've watched the entire video and still don't understand.