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ceslayer
Newbie
Joined: 15 Jul 2003 Posts: 15

Posted: 24 Feb 2004 02:01:21 am Post subject: 


OK, I have started a science sigfig program, addition part of it is almost done, BUT i have this problem.
when doing sigfig with an obsolute number , like 750 + 11.22, teacher told us to round off to the last precise place value, so 761.22 will become 760, since 750 is only precise to the tenth.
so how do i do that in ti83??@@ 
right now i ask user to input 2 values x and y and store them as strings.
then call sub( , instring(, but how could i tell calculator which is the
"least precise " place value? 

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ceslayer
Newbie
Joined: 15 Jul 2003 Posts: 15

Posted: 24 Feb 2004 02:02:30 am Post subject: 


and also, least precise to which part?
thanks! 

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Jedd 1980 Pong World Champion
Elite
Joined: 18 Nov 2003 Posts: 823

Posted: 24 Feb 2004 02:21:48 am Post subject: 


Easiest way to do what you are asking is to go to [Mode],[Down], and then select the number of decimal places you want to use.
However you may want to find out how many decimal places a number has from within the program. Here's my idea from off the top of my head:
Let's say your variable, A, is 11.2265. Now round the number to the nearest integer and test to see if it is equal to the original number. In this case, rounding to the nearest # would be 11. Since 11 does not equal 11.2265, it moves down 1 digit and tests that (If 11.2=11.2265) until it finds one that works (If 11.2265=11.2265). That way you can find the # of decimal places. For a sigfig calculator, you would need to test each number in the expression, and whichever one has the least is how many decimal places would be in the answer. 

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Arcane Wizard `semihippie`
Super Elite (Last Title)
Joined: 02 Jun 2003 Posts: 8993

Posted: 24 Feb 2004 08:24:23 am Post subject: 


ceslayer, please don't doublepost.
If you have the . in the string, you can just instring(str0,".") and then replace all the numbers after instring(str0,".")1 with 0's. 

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Fr0sty
Member
Joined: 27 Nov 2003 Posts: 202

Posted: 24 Feb 2004 11:18:51 am Post subject: 


Doesn't Round( do this? 

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tyskis
Member
Joined: 20 Nov 2003 Posts: 238

Posted: 24 Feb 2004 01:03:26 pm Post subject: 


don't know if you know this, but there is a calculator that does this in the "science tools" (i think that was the name) app from TI. Just a thougt... 

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robertak
Member
Joined: 14 Feb 2004 Posts: 125

Posted: 24 Feb 2004 07:39:35 pm Post subject: 


Quote: Doesn't Round( do this? Yes, you write round(number, number of numbers after
for example:
Code: input A
round(A,2
if you write 123.456, it will give you 123.46 because you specified 2 in the round( fonction
does it help? 

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Ray Kremer
Member
Joined: 16 Feb 2004 Posts: 237

Posted: 25 Feb 2004 02:17:45 pm Post subject: 


I maintain that using a program to do your sig figs thinking is more trouble than just learning the bloody sig figs rules, but there are a few such programs out there. Here's one for the 86, you can check how he did it.
BTW, you shouldn't assume that 750 only has two sig figs. Written like that, it could have three. This is where scientific notation helps. The difference between 7.5*10^2 and 7.50*10^2 is more clear. 

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Jeremiah Walgren General Operations Director
KnowItAll
Joined: 24 May 2003 Posts: 1937

Posted: 25 Feb 2004 02:37:46 pm Post subject: 


That's kind of the standpoint my teacher has. (Well, all of them.) Anyway, I think it's better if you know what's going on in the first place. Then just use your calculator to check your work. I've done that for the last four math tests I've taken, doing the work by hand and checking with my calculator, and I got an A on all of them.
It's been a little while since I've dealt with sigfigs. Perhaps I need to brush up on them a bit... 

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