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Topic: [math-learn] significant digits
Replies: 16   Last Post: Feb 28, 2002 7:49 PM

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Suzanne Alejandre

Posts: 113
Registered: 12/3/04
Re: [math-learn] significant digits
Posted: Feb 28, 2002 1:31 PM
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Well, I guess I can't get away without continuing with how I solved
this problem. :) I didn't convert the meters/second to miles/hour.
Instead I stopped at that point that I had a list of all of the
speeds using either 4 or 5 significant digits and I changed the 25
miles/hour to meters/second in order to make my conclusions.

Suzanne

>In a message dated 2/28/2002 12:17:09 PM Eastern Standard Time,
>suzanne@mathforum.com writes:
>
>

>> This time 2:20.8 (minutes: seconds) is 140.8 seconds
>> If you divide 1500 meters by 140.8 seconds you get 10.653409 meters/second
>> Because you start with 140.8 (4 significant digits) then the thought
>> is you would round off that answer to 10.65 meters/second.
>>
>> I could continue, but it is that "rounding off" part that I'm
>> interested in discussing.
>>

>
>
>Rounding off should always be the LAST thing you do before you put the box
>around your answer. Computations should be done with at least one more
>significant digit than you want in your final answer.
>
>
>You should continue the computation 10.653409 * 1 mile / 1609.344 meters *
>3600 seconds / 1 hour = 23.83099723 miles / hour < 25 and really no round off
>necessary to answer your question. Rounding now gives 23.83 miles / hour.
>
>Assuming 1500 is correct to at least four digits, 140.8 has four, 3600 is
>exact, the 1s are exact and 1609.344 has seven. The answer is accurate to no
>more than four digits. However to answer the speed limit question (< or >)
>you need even less.
>
>
>Lin
>
>Lin McMullin
>Niantic, CT.


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