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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
`semi-hippie`


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... Neutral
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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? Very Happy
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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


Know-It-All


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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