If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Lesson 2: Strategies for adding within 1,000

# Addition using groups of 10 and 100

Sal rewrites addition problems to make them easier to solve.

## Want to join the conversation?

• so if he were taking 10 away from 710 then why would you add 10 back to the number you were subtracting 10 from? That is the answer I'm giving you
(1 vote)
• i don uander stan can you halp my to uander stan? plais
• u just need to differentiate the different numbers so that u can make them easy to add.

So lets say u wanna add 257 + 593

so to do that in easy way, we can take some of the unit digit to the other number so we get 0 at units digit or more as it will be easy to add then

so 257+593 = 250+(7+593) (we moved the seven from 257 to 593)

so (257-7)+(593+7)

=250+600 = 850 (so now its easy to add)

I hope it helps

Nuclear Studios
• do you give the ones to the number
• 138 + 710 = __ + 700
In the right hand side, 10 has been removed from 700.
Therefore, the removed 10 must be added to 138 i.e.,
138 + 10 = 148 is the answer
• Lily has 500000 pennys and man has 40000 how much do they have in all
• 900000 pennys
• how does this help me I dont understand this stuff!
• Don't worry if you don't understand this method! Different things work for different people, so ask your teacher or somebody else for a different way to do this.
Or, if you really want to understand this, ask them to help you through the steps of it until you understand.
• Everybody its mostley rounding.
This is a good strategy for our level.
• Everybody. It’s mostley rounding this is a. Good strategy for our level
• what is 10000000 times 9
• 90000000

If you're writing it out on a piece of paper:

10000000
X 9
--------
90000000

Hope that helps!
• How would this work when adding thousands.
• Similar to the first question in the video at , 632 + 4278 could be done like this:
(630+2)+4278
630+(2+4278)
630+4280

This equals 4,910. It's a bit more difficult in the thousands, but it can still be done in the same way.