## knowing how many sig figs to use

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Peter Nguyen 2I
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Joined: Fri Sep 28, 2018 12:29 am

### knowing how many sig figs to use

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?

Selina Bellin 2B
Posts: 62
Joined: Fri Sep 28, 2018 12:25 am

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

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!

Hannah Morales 1D
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Joined: Fri Sep 29, 2017 7:06 am

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

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!

Michael Novelo 4G
Posts: 64
Joined: Fri Sep 28, 2018 12:28 am

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

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.

Alexandra Ortega 4D
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Joined: Wed Oct 03, 2018 12:17 am

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

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.

Nell Mitchell 1E
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Joined: Fri Sep 28, 2018 12:16 am

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

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)

Nell Mitchell 1E
Posts: 31
Joined: Fri Sep 28, 2018 12:16 am

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

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)

josephperez_2C
Posts: 70
Joined: Wed Nov 15, 2017 3:04 am

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

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.

SophiaKohlhoff4B
Posts: 30
Joined: Fri Sep 28, 2018 12:16 am

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

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.

Lily Benitez 2G
Posts: 63
Joined: Fri Sep 28, 2018 12:29 am

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

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.

Alan Chang
Posts: 33
Joined: Fri Sep 28, 2018 12:29 am

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

Its also important that during addition or subtraction, the value with the least amount of decimal spaces should be used instead of sig figs.

vaishali 1D
Posts: 61
Joined: Fri Sep 28, 2018 12:19 am

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

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.

Lia Inadomi 1I
Posts: 62
Joined: Fri Sep 28, 2018 12:15 am

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

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?

Marwan Masri 3B
Posts: 31
Joined: Fri Sep 28, 2018 12:23 am

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

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.

Mikka Hoffman 1C
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Joined: Fri Sep 28, 2018 12:23 am
Been upvoted: 2 times

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

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

Nicholas Kull_3L
Posts: 30
Joined: Fri Sep 28, 2018 12:23 am

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

yes that is two sig figs and usually you base it off how many sig figs are in the question asked.

Liza Hayrapetyan-3K
Posts: 31
Joined: Fri Sep 28, 2018 12:25 am

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

Also, remember to ignore any zeros in the beginning!

I am Sodium Funny
Posts: 65
Joined: Fri Sep 28, 2018 12:26 am

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

General rule of thumb: Go by the fewest amount of sig figs for any givens!

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