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### knowing how many sig figs to use

Posted: Fri Oct 05, 2018 4:35 pm
I am still a bit confused on significant figures and when to use a certain number of sig figs. Will the answer to a problem always have the same number of sig figs as in the question?

### Re: knowing how many sig figs to use

Posted: Fri Oct 05, 2018 4:38 pm
the appropriate amount of sigfigs to use in an answer is the least amount of sigfigs. so if a question has 3 values, 3.08, 4.204 and 9.02, 3 sigfigs are the appropriate amount to use in your result. hope this makes sense!

### Re: knowing how many sig figs to use

Posted: Fri Oct 05, 2018 4:40 pm
I tend to think that with sig figs it is the smallest amount of units in a number from the question. So say if in a question the mass of something is 3.01g, you sig figs for your answer should be three units because in this instance, there is three units in the question. Sorry if that wasn't much help!

### Re: knowing how many sig figs to use

Posted: Fri Oct 05, 2018 5:35 pm
Usually the problem gives you a certain amount of a element or substance to start off with for example 8.00 g of Fe and it would ask you to solve for another variable. In this case use the 8.00 g Fe as a reference point to how many sig figs your answer will be in this case it will be 3 sig figs. It's also good to use appropriate sig figs when dividing or multiplying when solving for an answer so it's more precise to the actual answer.

### Re: knowing how many sig figs to use

Posted: Sun Oct 07, 2018 5:48 pm
The number of sig figs that you should have in your answer is usually the number of sig figs given in the numerical values in the problem you are solving, unless it otherwise specified. If you are given 140. kg then your final answer should also have 3 sig figs. In addition, you should not round to a certain number of sig figs until your final answer to maintain accuracy. So, you want to keep all numbers that you calculate until the very end.

### Re: knowing how many sig figs to use

Posted: Sun Oct 07, 2018 9:01 pm
It's also important to note that leading zeros don't count as sig figs (ie 0.000234 has 3 sig figs) and that non-placeholder zeros to the right of a decimal do count as sig figs (ie 21.200 has 5 sig figs)

### Re: knowing how many sig figs to use

Posted: Sun Oct 07, 2018 9:09 pm
It's also important to note that leading zeros don't count as sig figs (ie 0.000234 has 3 sig figs) and that non-placeholder zeros to the right of a decimal do count as sig figs (ie 21.200 has 5 sig figs)

### Re: knowing how many sig figs to use

Posted: Sun Oct 07, 2018 9:52 pm
You should use the amount of significant figures in your answer that corresponds with the least amount of significant figures in any one given value of the problem.

### Re: knowing how many sig figs to use

Posted: Sun Oct 07, 2018 10:42 pm
For problems involving multiplication/division, the product/quotient should be rounded to the least number of sig figs of the factors. For problems involving addition/subtraction, the sum/difference should be rounded to the least number of sig figs after the decimal.

### Re: knowing how many sig figs to use

Posted: Sun Oct 07, 2018 10:46 pm
What helps me when it comes to sig figs I usually put the numbers given into scientific notation. This helps when the numbers are too big or too small to tell the appropriate sig figs.

### Re: knowing how many sig figs to use

Posted: Sat Oct 13, 2018 3:50 pm
Its also important that during addition or subtraction, the value with the least amount of decimal spaces should be used instead of sig figs.

### Re: knowing how many sig figs to use

Posted: Sun Oct 14, 2018 11:13 am
Peter Nguyen 4B wrote:I am still a bit confused on significant figures and when to use a certain number of sig figs. Will the answer to a problem always have the same number of sig figs as in the question?

For addition and subtraction, you want to use the least number of decimal points from the values given to you in the question. For multiplication, you use the least number of sig figs from the given values.

### Re: knowing how many sig figs to use

Posted: Tue Oct 16, 2018 6:32 pm
What does it mean when there is a period after a number but no decimals after the period? For example, 50. g of something. Is that still 2 sigfigs?

### Re: knowing how many sig figs to use

Posted: Fri Oct 19, 2018 9:18 am
Lia Inadomi 1I wrote:What does it mean when there is a period after a number but no decimals after the period? For example, 50. g of something. Is that still 2 sigfigs?

yeah that's two sig figs.

### Re: knowing how many sig figs to use

Posted: Fri Oct 19, 2018 9:59 am
If you're still confused on sig fig rules, this is a helpful resource for what Dr. Lavelle expects with significant figures: https://lavelle.chem.ucla.edu/wp-conten ... OUT_SF.pdf

### Re: knowing how many sig figs to use

Posted: Fri Oct 19, 2018 10:46 am
yes that is two sig figs and usually you base it off how many sig figs are in the question asked.

### Re: knowing how many sig figs to use

Posted: Sat Oct 27, 2018 10:08 pm
Also, remember to ignore any zeros in the beginning!

### Re: knowing how many sig figs to use

Posted: Sat Oct 27, 2018 10:25 pm
General rule of thumb: Go by the fewest amount of sig figs for any givens!