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Topic: Simple Sig Figs Question  (Read 3526 times)

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Offline StayOnTop

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Simple Sig Figs Question
« on: November 16, 2010, 10:55:17 PM »
OK, let's say I compute a number to be 13.48, but I need it to be to two significant figures. Would I round the number to 13.5, and then 14. (with 14 being the final, two sig fig answer). Or, would I just immediately round it to 13., without worrying about rounding the .4 to .5 (due to the 8 in the hundreths place).

I guess I should give the total answer.

I have .075=0.00341X + 0.029
I first subtract .075 -.029= .046
Then, I divide .046/.00341=  13.489736

I rounded to 13.5, then to 14. for the final two sig figs. Am I right? Thanks for any help.

Offline rabolisk

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Re: Simple Sig Figs Question
« Reply #1 on: November 16, 2010, 11:04:36 PM »
You would round it down to 13.

Offline StayOnTop

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Re: Simple Sig Figs Question
« Reply #2 on: November 16, 2010, 11:15:06 PM »
You would round it down to 13.
Really? So, in this case, the 5 in the hundreths place has no bearing on the 4 in the tenths place?

Offline rabolisk

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Re: Simple Sig Figs Question
« Reply #3 on: November 16, 2010, 11:33:40 PM »
The idea that you would round 13.48 to 13.5 then to 14 doesn't make much sense. Clearly 13.48 is closer to 13 than to 14. In general to round, you simply look at the next digit and round down if it is <5, and up otherwise.

Offline StayOnTop

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Re: Simple Sig Figs Question
« Reply #4 on: November 16, 2010, 11:45:37 PM »
Yes, but isn't 13.48 closer to 13.5 than 13.4, and thus wouldn't you round up to 14?

Offline rabolisk

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Re: Simple Sig Figs Question
« Reply #5 on: November 17, 2010, 12:44:09 AM »
Yes, 13.48 is closer to 13.5 than 13.4, but closer to 13 than 14.

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