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Date: 9/9/96 at 22:1:45
From: Anonymous
Subject: Little (stupid) mistakes

Dr. Math,

I've had problems keeping myself from doing little mistakes such
as not putting commas in, putting the decimal point in the wrong
place, and writing down the wrong number (though I HAVE gotten better
about that!).  I've tried to check over everything, but I still end up
making those mistakes (I have to admit, I DO do better if I check over
everything)!  How can I stop doing this?

Jennifer
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Date: 9/10/96 at 19:56:40
From: Doctor Tom
Subject: Re: Little (stupid) mistakes

Hi Jennifer,

There are a few things you can do:

or into the problem to see if it works.

For example, if you're solving for x in: 5x - 3 = 17,
and you get x = 5, try it out:  5*5 - 3 = 17?  25-3 = 17? 22=17?
Nope!

2)  This method works better for word problems than equations,
and that's to try to get a feeling for what the answer should
be before you work it out (at least roughly).  Then see if the
answer you get is out of the ballpark.  For example, suppose
you're talking about a trip to the store, and you buy items
costing \$1.76, \$2.43, \$5.01, \$11.43, ... about 10 items like
that.  What's the total cost?  Take a look at all the numbers.
In this case, it looks like the rough "average" (just by
about \$50 is roughly right.  If you get \$500 or \$5, you know
you're out of the ballpark.

3)  If you can figure out how to do a problem in more than
you can do this.  For example, when I'm adding up the
I'll do it twice, but once I'll start typing them into the
calculator from the top of the list to the bottom, and the
next time, I'll type them in from bottom to top.  If I do
it the same way both times, I'm much more likely to make
the same mistake both times.

I hope this helps some.

-Doctor Tom,  The Math Forum
Check out our web site!  http://mathforum.org/dr.math/
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