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When
we add small numbers together, |
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we
can count them on our fingers. |
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We
can count up little dots in our minds. |
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But
after a while, |
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most
people memorize little addition problems. |
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Problems
like ... |
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That's
fine for small stuff. |
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What
about stuff like: |
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Nobody
memorizes that one! |
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So
here's what you do. |
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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 |
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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. |
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| Go one
column to the left and add up those numbers: |
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Well
great, |
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but
what about when the numbers in the column add up to more then
nine? |
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What
do we do THEN? |
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Well? |
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Glad
you asked. OK, say you have: |
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Maybe
we know that 8 + 7 = 15. |
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For
now, we only write down the least valuable digit |
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(remember
the place value stuff?). |
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That means we
write down the 5
and hold on to the one for a bit. |
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The
1 (that actually means 10) goes into the tens column. |
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The
tens column is the next column to the left. |
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If
there are other numbers there already, |
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the
one gets added to them. |
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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! |
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Write down
the zero at the bottom
of the column,
and put the 1 on the top
of the next column to the left. |
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Add up the
numbers in the column.
1 + 1 = 2.
Write it down.
There's no more numbers so we're done. |
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Let's
do one more ... |
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Example: |
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Step 1:
6 + 7 = 13.
Write down the 3.
Put the 1 on top of the 5 in the next column
to the left. |
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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.
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Step 3:
1 + 3 = 4.
Write down the 4.
We're out of numbers so we're done. |
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copyright 2005 Bruce Kirkpatrick |
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