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## Class 3

### Course: Class 3>Unit 5

Lesson 1: Adding by carrying over

Sal shows some techniques for doing mental addition, such as making groups of 10 and 100.

## Want to join the conversation?

• When adding two numbers, one good trick is 1) subtracting something from one number and adding the same thing to the other number (think of trading) to make new numbers that are easier to add, and then 2) adding the new, easier numbers. Adding the new numbers will give the same answer as adding the original numbers.

So we could subtract 40 from 345 to get 305, and add 40 to 564 to get 604.
The new addition problem becomes 305 + 604, which is a much easier addition problem. The answer is obviously 909.
So 345+564 = 909.

Have a blessed, wonderful day!
• what is 800+200
• 800 + 200 = 1000, it's really simple think of it as 8 + 2 + 2 extra 0's at the back! :)
• how do you add 355 whith 480
(1 vote)
• Try to learn easy methods. Such as break the terms and then add. For example:
``Ones``
5 and 0 equals 5 ones.
``Tens``
5 and 8 equals 13 tens that further equals 1 hundred and 3 tens.
``Hundreds``
3 and 4 equals 7. Now add the previous hundred in it and you'll get 8 hundreds.

The answer is 8 Hundreds, 3 Tens and 5 ones.
In short 835.