## Sig figures

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### Sig figures

How many sig figs should you write your answer using if a question has two numbers with a differing amount of sig figs?

Susu Le 1F
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### Re: Sig figures

The number of sig figs in your answer should be the least number of sig figs that is given in the question.

Chem_Mod
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### Re: Sig figures

It depends on the mathematical operation you perform. The final answer is always not the least number of sig figs given to you. A counter example is 2.37 + 0.15 = 2.52 (3 sig fig, despite adding 2 and 3 sig fig numbers). So to do the significant figures correctly, you would have to know the rules for the different mathematical operations you perform.

AnnaYan_1l
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### Re: Sig figures

There are different rules for different operations. Multiplication and division are pretty straight forward, but addition and subtraction are a little bit different.

Multiplication and division: Round to the least number of significant figures of the numbers in the problem. (ex. 3.5 * 2.03 = 7.1)

Addition and subtraction: Look at the decimal portion (the numbers to the right of the decimal). After adding or subtracting, round the answer to the least number of places in the decimal portion of the numbers in the problem. (ex. 3.5 + 2.03 = 5.5)

Hope that helps!

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Joined: Fri Apr 06, 2018 11:03 am

### Re: Sig figures

If you're adding, you use the number with the least number of decimal places as your determinant for the number of decimal places for your answer. Meanwhile, if you're multiplying, the one with the least number of SF should be used to determine the number of SF for the answer.

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### Re: Sig figures

If you're adding, you use the number with the least number of decimal places as your determinant for the number of decimal places for your answer. Meanwhile, if you're multiplying, the one with the least number of SF should be used to determine the number of SF for the answer.

Sonia Aronson 1B
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### Re: Sig figures

How do you know how many decimals to use? For example, if I had 2.0 moles x 134.6 g, how many decimals should my answer have?

304984981
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Joined: Fri Apr 06, 2018 11:05 am

### Re: Sig figures

if in the question the number is 0.500g for example， then all your calculation must be in 3 significant figures.

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### Re: Sig figures

Sonia Aronson 1B wrote:How do you know how many decimals to use? For example, if I had 2.0 moles x 134.6 g, how many decimals should my answer have?

If you had 2.0 mol x 134.6 g/mol, your answer should have two decimal places (2.692 g --> 2.7 g). This is because when you multiple or divide, you count the number of Sig Figs in each given number and you use the lowest number of Sig Figs in your answer.

Megan Phan 1K
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Joined: Fri Apr 06, 2018 11:04 am

### Re: Sig figures

The amount of significant figures you need is dependent on the equation you're solving. The number you use is the least number of decimal places for your answer. However, it is not always the case, you need to know the proper mathematical operation rules to determine case by case.