Q&A #1154

Teachers' Lounge Discussion: Front End Estimation

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From: Loyd

To: Teacher2Teacher Public Discussion
Date: 2001091803:16:36
Subject: Re: Front End Estimation

Estimation may not be an exact science and I don't think we should be
too hung up on the exactness of the process.  I have heard professors
chastise students because he/she didn't estimate their answers. 
Frequently, one sees a student in science such as physics or physical
science or chemistry, turn in an answer in the thousands when the
answer should have been in the tens or hundreds.  The estimation is
used by many professional people to make sure they are in the ballpark
so they won't have a "misplaced decimal" type mistake.  I have made
stupid mistakes and often estimate my answers to help avoid these
embarrassing mistakes.  

My wife has some experience in accounting.  For years she has added to
the nearest 10 cents while shopping.  Thus if bread is 1.30 she
thought 13.  Then when she got butter for 1.90 she would think 19 and
add to the 13 mentally.  One Sunday evening we went into a small store
and bought about 10 dollars worth of groceries.  The clerk punched it
into his machine and said 14.00 or there about.  He hadn't given her a
tape and she said she had calculated about $10.00 and she asked him to
run a tape.  He did and my wife was right.  It pays to be able to

I suspect she could have added to the nearest quarter and come pretty
close to the answer. That would be 5+8 =13 quarters which is $3.25. 
This estimate is only 5 cents off the actual amount.  

The clerk should have given her a tape, of course. The incident I just
described was the first time I knew that my wife performed this mental

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