Which number determines sig figs of the answer?

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Rob Tsai 2F
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Which number determines sig figs of the answer?

Postby Rob Tsai 2F » Wed Oct 07, 2020 2:00 pm

If a question with numbers such as 8.25 g/mol and 9.2 grams, would significant figures of the answer be determined by the greater number of sig figs in 8.25 or the smaller number in 9.2?

Chem_Mod
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Re: Which number determines sig figs of the answer?

Postby Chem_Mod » Wed Oct 07, 2020 2:05 pm

It depends on what operation you use. In the case of multiplying them, then the number of significant figures would be determined by the one with the smaller number of sig figs.

Joey_Okumura_1E
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Re: Which number determines sig figs of the answer?

Postby Joey_Okumura_1E » Wed Oct 07, 2020 2:19 pm

When multiplying or dividing, the sig figs will be equal to the number of sig figs in the least precise measurement. When subtracting or adding, the the result should have the same number of decimal places as the least precise measurement.

Kamille Kibria 2A
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Re: Which number determines sig figs of the answer?

Postby Kamille Kibria 2A » Wed Oct 07, 2020 6:24 pm

it depends on what operations you are using throughout the problem. for adding/subtracting, the # of sig figs in the answer is determined by the value that has the least amount of number AFTER the decimal point. however, for multiplication/division, the # of sig figs in the answer is determined by the value with the least amount of sig figs (so 9.2). usually if there is both addition/subtraction and multiplication/division in a problem, I was told that your best bet is to go with the value with the least amount of sig figs, especially if it was already given in the problem. hope that helps :)

Ethan Goode 2H
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Re: Which number determines sig figs of the answer?

Postby Ethan Goode 2H » Wed Oct 07, 2020 6:44 pm

For this example, if multiplying or dividing, whatever the number with the smallest amount of significant figures will determine how many sig figs will be in your final answer.

Jonathan Batac - 2D
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Re: Which number determines sig figs of the answer?

Postby Jonathan Batac - 2D » Wed Oct 07, 2020 7:40 pm

In chemistry, there are two sets of operations with different rules when it comes to significant figures. With multiplication/division, the resulting answer will depend on the value of the least amount of sig figs; in this case, two significant figures (9.2). With addition/division, the resulting answer will have the same number of decimal places as the original number with the fewest decimal place; in this case, one decimal place (9.2).

Mackenzie Stockton 2H
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Re: Which number determines sig figs of the answer?

Postby Mackenzie Stockton 2H » Wed Oct 07, 2020 9:53 pm

Supporting what others have said, the number of sig figs depends. For multiplication and division, use the smallest number of overall sig figs. For addition and subtraction, you look at the smallest number of decimal places and

Juwon Lim 2A
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Re: Which number determines sig figs of the answer?

Postby Juwon Lim 2A » Wed Oct 07, 2020 10:03 pm

Generally, you want to use the least precise measurement to determine how many sig figs your answer will have. When multiplying/dividing, your answer should have as many sig figs as the measurement given that has the least sig figs. When adding/subtracting, your answer should have as many decimal points as the measurement given that has the least sig figs. Remember not to round in between calculations in order to be as accurate as possible!

Charisma Arreola 2F
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Re: Which number determines sig figs of the answer?

Postby Charisma Arreola 2F » Wed Oct 07, 2020 10:23 pm

Do you know where we can find the rules for the sig figs? Like a completed list that has them simplified?

Adalia 3E
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Re: Which number determines sig figs of the answer?

Postby Adalia 3E » Wed Oct 07, 2020 10:26 pm

Charisma Arreola 2L wrote:Do you know where we can find the rules for the sig figs? Like a completed list that has them simplified?

https://lavelle.chem.ucla.edu/wp-conten ... OUT_SF.pdf This PDF is the one on Lavelle's website, and there's a few other resources there as well

Lauren Sarigumba 1K
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Re: Which number determines sig figs of the answer?

Postby Lauren Sarigumba 1K » Wed Oct 07, 2020 11:56 pm

For addition/subtraction problems, your final answer may have no more significant figures to the right of the decimal than the LEAST number of significant figures in any decimal portion of any number in the problem. For multiplication/division, the LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer (you are now looking at the entire number, as opposed to just looking at the decimal portion you would normally look at for addition/substraction problems)

Joanna Huang
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Re: Which number determines sig figs of the answer?

Postby Joanna Huang » Fri Oct 09, 2020 4:45 am

For any operation, just think LEAST. For adding/subtracting, you look for the least number of sig figs to the right of the decimal. For multiplying/dividing, you go for the least amount of sig figs in general.

Peter DePaul 1E
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Re: Which number determines sig figs of the answer?

Postby Peter DePaul 1E » Fri Oct 09, 2020 6:48 am

For example if it was the answer would be 58.4. If you were doing something like the answer would be
13.3

Binyu You
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Re: Which number determines sig figs of the answer?

Postby Binyu You » Fri Oct 09, 2020 8:29 am

I think for addition or subtraction, the answer of the question should have equal number or less significant figures than the number with the least significant figures in the question. In the case of multiplication or division, the answer should have the same amount of significant figures with the number that has the least amount of significant figures.

Luveia Pangilinan 1A
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Re: Which number determines sig figs of the answer?

Postby Luveia Pangilinan 1A » Fri Oct 09, 2020 8:43 am

I don't really know how to post a new topic but it is related to this forum anyway so I'm just gonna ask it here. If a problem asks you to do both multiplying/dividing and adding/subtracting, what sig fig rule do you follow?

Pranav Daggubati 3C
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Re: Which number determines sig figs of the answer?

Postby Pranav Daggubati 3C » Fri Oct 09, 2020 9:37 am

Usually, the number with the least amount of sig figs determines how many sig figs you can use.

Inderpal Singh 2L
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Re: Which number determines sig figs of the answer?

Postby Inderpal Singh 2L » Fri Oct 09, 2020 10:55 am

Based on what I learned from my chem teacher in highschool, we usually just went with the smallest number given to us in the actual problem.

AustinMcBrideDis3L
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Re: Which number determines sig figs of the answer?

Postby AustinMcBrideDis3L » Fri Oct 09, 2020 10:58 am

Typically in cases of chemistry you will have some type of multiplication or division in your problem and as a result you will just use the smallest amount of sig figs in the givens as the amount in your answer. (but follow the rules others have given above if your problem happens to only include addition/subraction).

Keshav Patel 14B 2B
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Re: Which number determines sig figs of the answer?

Postby Keshav Patel 14B 2B » Fri Oct 09, 2020 11:37 am

When you are multiplying it is determined by the number with the least amount of significant digits.

Jonathan Malau 1F
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Re: Which number determines sig figs of the answer?

Postby Jonathan Malau 1F » Fri Oct 09, 2020 3:42 pm

While I understand the procedure, why is it that being able to round to a significant figure important in chemistry?

Anthony_Sandoval_1D
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Re: Which number determines sig figs of the answer?

Postby Anthony_Sandoval_1D » Fri Oct 09, 2020 11:31 pm

The number with the least amount of figures determines the sig figs.

rita_debbaneh2G
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Re: Which number determines sig figs of the answer?

Postby rita_debbaneh2G » Sat Oct 10, 2020 9:32 am

This depends on the operation. When adding or subtracting, look for the value with the least amount of numbers in the decimal place. Your answer will have that same number of digits after the decimal point. For example, if you're subtracting 17.923-6.6, your answer will be 11.3. Note the single value after the decimal place. If you're multiplying or dividing, your answer should have the same number of sig figs as the value with the least amount. For example, if you're multiplying 82.891 and .045, then your answer will be 3.7.

Mariah Disc 2C
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Re: Which number determines sig figs of the answer?

Postby Mariah Disc 2C » Sat Oct 10, 2020 11:44 pm

In general, I was told that it is best to go with the least amount of sig figs in the problem. It does however depend on what operations you are using throughout the problem.

Katelyn_Ortega_1D
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Re: Which number determines sig figs of the answer?

Postby Katelyn_Ortega_1D » Sat Oct 10, 2020 11:51 pm

It depends on the operation of course, however a rule of thumb I always used was to go by the number that had the least number of significant figures

Cooper_Geralds_3B
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Re: Which number determines sig figs of the answer?

Postby Cooper_Geralds_3B » Sat Oct 10, 2020 11:53 pm

The significant figure depends on what the specific question is asking for, if the question specifically asks about moles then you would refer to the sig fig of the moles given and used throughout the problem.

joshtully
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Re: Which number determines sig figs of the answer?

Postby joshtully » Sun Oct 11, 2020 5:13 pm

What should be done if the smallest number in the problem has 1 sig fig, and the answer is something like 1432 g? Should we round to 1000 g since that would be 1 sig fig?

205323697
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Re: Which number determines sig figs of the answer?

Postby 205323697 » Sun Oct 11, 2020 11:30 pm

Adding and subtracting have the same rule, after getting your answer you want to use the significant figure of the number that has the least set of numbers after the decimal. When you are multiplying or dividing you want to use the number with the least amount of significant figures.


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