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Sig Figs for Question 8.45 (a)

Posted: Sat Jan 13, 2018 4:30 pm
by Tia Tomescu 2D
My answer was 448.5 which I rounded to 449. But the answer was 448. Does anyone know why?

Re: Sig Figs for Question 8.45 (a)

Posted: Sat Jan 13, 2018 4:39 pm
by Ozhen Atoyan 1F
My guess would be that it is because of something in your calculations. I would say it might be a rounding error. My advice would be to complete all the steps of the problems and round at the end. Rounding in the middle may give you slightly different numbers.

Re: Sig Figs for Question 8.45 (a)

Posted: Sat Jan 13, 2018 5:12 pm
by Hubert Tang-1H
I've also gotten the answer of 448.5 kJ, rounded to 449 in my calculations. It doesn't seem to be due to be a rounding error, as you get the answer 448.5 kJ from only one equation.

In addition, this situation also appears to occur in other answers I've gotten here and there. How accurate do we need to be in our answers for these HW problems to be counted as correct? (For example, is +/- 1 off for the lowest significant digit okay?)

Re: Sig Figs for Question 8.45 (a)

Posted: Sat Jan 13, 2018 5:58 pm
by Christina Bedrosian 1B
I've heard that if the answer ends in .5, you would round to the nearest even number, which in this case would be 448. I am not sure if this is the official rule to go by but I remember reading it in 14A so maybe that would explain it.

Re: Sig Figs for Question 8.45 (a)

Posted: Sat Jan 13, 2018 8:16 pm
by Kellina Tran 2I
Dr. Lavelle has mentioned in class before that his method is to round to the nearest even number if it ends in a 5, so I would assume that is the way he would prefer it to be on exams/tests. I doubt you would get docked off points for rounding it to 449 though.

Re: Sig Figs for Question 8.45 (a)

Posted: Sat Jan 13, 2018 8:28 pm
by Marina Georgies 1C
Although most math classes teach the rule that .5 or 5 rounds up, another commonly accepted method is to round to the nearest even number. I think the method of rounding commonly used in chemistry is the second one, as mentioned in the previous replies. So they are correct about rounding a 5 or .5 to the nearest even number, even if that means rounding down.