Pre Algebra Addition Carrying
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Pick It Up
Addition Carrying

 
 When we add small numbers together, 
 we can count them on our fingers. 
 We can count up little dots in our minds.
 
 But after a while,
 most people memorize little addition problems.
 
 Problems like ...
 

 
 That's fine for small stuff. 
 What about stuff like:
 

 
 Nobody memorizes that one! 
 So here's what you do.
 

Start with the lowest value digits 
(the ones all the way to the right). 
Add them up. 
If they add up to less than ten, great. 
Just write that down and go on

 
Move one column to the left 
and add up the digits. 
If they add up to nine or less, 
great, write it down and go on.

 
Go one column to the left and add up those numbers:

 
 Well great, 
 but what about when the numbers in the column add up to more then nine? 
 What do we do THEN? 
 Well?
 
 Glad you asked. OK, say you have:
 

 Maybe we know that 8 + 7 = 15. 
 For now, we only write down the least valuable digit
 (remember the place value stuff?).
  
That means we write down the 5 
and hold on to the one for a bit.

 

 The 1 (that actually means 10) goes into the tens column. 
 The tens column is the next column to the left. 
 If there are other numbers there already, 
 the one gets added to them.
 
Write the one on the top of the tens column. Then add up the numbers in the column. 
1 + 8 + 1 = 10 
Here we go again!

 
Write down the zero at the bottom 
of the column, 
and put the 1 on the top 
of the next column to the left.

 
Add up the numbers in the column.
1 + 1 = 2. 
Write it down. 
There's no more numbers so we're done.

 
 Let's do one more ...
 
 Example:
 

 
Step 1: 
6 + 7 = 13. 
Write down the 3
.
Put the 1 on top of the 5 in the next column
to the left.

 
Step 2:
1 + 5 + 8 = 14. 
Write down the 4
.
Put the 1 on top of the 3 in the next column
to the left.

 
Step 3:
1 + 3 = 4. 
Write down the 4. 
We're out of numbers so we're done.

 

   copyright 2005 Bruce Kirkpatrick

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