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Subtracting Big Numbers

Date: 11/20/95 at 8:2:14
From: Anonymous
Subject: What's 245715 - 105065 ?

What's 251715
     - 105065 ?

Date: 12/10/95 at 19:35:14
From: Doctor Ken
Subject: Re: What's 245715 - 105065 ?


To do this question, keep in mind that when you do subtraction with 
really big numbers, it's no different from doing it with smaller ones, 
it just takes longer.  So I'll get you started, and see if you can take 
it from there.

The first step we do is pretty easy: the digits on the right are both 5, 
so since 5 - 5 = 0, we just write a zero down below:


The next part is a little trickier, though.  Since 1 is less than 6, 
we'll have to borrow from the 7 that's next to the 1.  So you'd cross 
out the 7 and make it a six (kind of hard to show here with typing!), 
and add ten to the 1 to make it an 11.  So now we have 11 - 6, and 
that's 5.  So we have

         1    (that 1 there is supposed to be next to the 1 
     251615    that's below it, to make it an 11)

Do you think you could take it from here?

-Doctor Ken,  The Geometry Forum

Associated Topics:
Elementary Subtraction

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