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Topic: Approximations
Replies: 2   Last Post: Feb 26, 1996 10:35 PM

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Tom Johnson

Posts: 62
Registered: 12/6/04
Approximations
Posted: Feb 23, 1996 1:04 PM
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At the risk of beating the approximation topic to death.....

Here is a quick and simple exercise to show students what the
basic problem is with calculators and computers.

Using pencil and paper, calculate ( 1 / 3 ) x 3.

Any student past the 5th grade should see that the threes in the
numerator and denominator cancel and that the answer is exactly ONE.

Now work the same problem on any calculator: 1/3 = 0.3333333, then
multiply by 3 to get (on a typical Wal-Mart variety calculator) 0.999999

Obviously, this little exercise can be extended...
(1/3) x 3 x (1/5) x 5 x ( 1/7) x 7 ... etc. The point
is that it is easy to get a "wrong" answer on a calculator
(although the magnitude of the error will vary depending upon
several things). The two questions one must always keep in mind
are 1. How accurate is my answer? and 2. How accurate does it
need to be?

TCP/IP-ingly yours.....

Tom Johnson, Gilberts, IL |"I know you smoke, I know you drink that brew, I
tjohnson@interaccess.com |just can't abide a sinner like you. God can't either
"Curb your dogma ... | that's why I know it to be true that Jesus loves me
free your thoughts." | but he can't stand you." Austin Lounge Lizards






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