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# Tips for Counting and Predicting Sig Figs - Concept

###### Kendal Orenstein

###### Kendal Orenstein

**Rutger's University**

M.Ed., Columbia Teachers College

Kendal founded an academic coaching company in Washington D.C. and teaches in local area schools. In her spare time she loves to explore new places.

Today we're going to talk about some tips, on counting and predicting the number of Sig Figs properly. I know this is a terrible rendition of United States of America, but this is actually the USA protasis. I'm sorry, it isn't represented very well. But anyway this instead of being the USA, it's the Land of Significance. I promise you, this will all make sense. It will all come together in just a second.

On the right of the Land of Significance, we have typically in the right of the United States, we have the Atlantic Ocean. Here we're going to talk about the Atlantic Ocean starts with an A, and we're going to say if the decimal is absent. We're going to start on the right hand side. On the left hand side, it's typically the Pacific Ocean, so we're going to use that side if the decimal is present.

What the heck am I talking about? So to understand this scenario that I've put in front of us, let's actually use some practice. So let's say I threw a number at you, and it was 200. I would like you to tell me how many significant figures it has.

Well, does 200 have a decimal place? No. So you are going to sail from the right hand side where the decimal place is absent. So we're going to put this in the Land of Significance. We're going to sail until we hit a non-zero. Once you hit a non-zero, everything to the left of that is significant. So this is significant. The 0's, not significant. So this 200 has one sig fig; and that's the 2.

How could I write that just using sig figs? Instead of writing 200, so I'm going to say 200 does not equal

200 anymore. Equals 2×10² . Then this is going to have units. Let's say it was grams. 2×10² g. Not 2.0×10²g,

because we do not want include those insignificant numbers. The only significant number in this is the 2. This

is another way we can write it.

Let's practice with another one. So let's say we have 207650cm. How many sig figs does that have in it? Well, again decimal place is absent so we're going to sail to the right until we hit a non-zero. So we're going to sail till we hit the 5. This 0 is insignificant. All of these numbers are significant. This is insignificant. Even though that there's a 0 there, it doesn't mean that it's not significant. So we have 1, 2, 3, 4, 5, 6 figs. Again, another way to write this is to say 2.0765×10 to the 4cm. This is our answer. Notice I did include the decimal places in this one because, they are all significant, but not the last zero.

So let's say the decimal place is present. Let's say it's there, we do have a decimal place. So let's say we do have the number. I'm going to say the number 2.700g. This time we're going to sail from the left hand side until we hit a non-zero. Same thing; sail and we hit a non-zero immediately. All of these numbers are significant. Which means we have 4 sig figs. So that's actually fine.

Let's say I give you another number 0.0720mL. Do the same thing. We're going to sail from the left, sail, sail, sail, we hit the non-zero here. These numbers are just place-holders, and not necessary. All these are significant. So we have 3 sig figs. If I were to represent this just using sig figs, I would again but using scientific notation, say 7.20, including that 0 because it is significant, times 10 to the -2 milliliters here. So this would be our practice number just using sig figs.

So actually instead of memorizing all those rules that you see sometimes in textbook, and you see sometimes when your teacher explains what a sig fig is, that can get a bit overwhelming, and a bit cumbersome. So this method is actually really easy, and it's fail-proof. It will never let you, and you can use this method every time when you're counting sig figs. This is will help you to get the correct answer when you're doing calculation. I hope this helped.

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###### Kendal Orenstein

M.Ed., Columbia Teachers College

Her energy is contagious. She gets you excited about learning new concepts and makes it easy to understand. Her love for chemistry comes across in all her videos.

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## Comments (7)

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## Madhur · 7 months, 1 week ago

Thank you, Lydia for explaining since I was waiting for Jwala's answer for so long but I think it could be more specific because according to your comment the above method is incorrect.

## Lydia · 11 months ago

To Jwala - I think math that is used in science should be in the most simplified form. The number 002 can be simplified to 2 thus only have 1 sig fig. This is probably not too often seen so its not included in the video.

## manasitiwari · 1 year, 2 months ago

You did not answer jwala [comment below] ,just because you dont know the answer.Is it true.

## Brightstorm · 1 year, 2 months ago

We believe in freedom of speech just as much as you do. That's why we only remove comments that contain inappropriate language or are spam. We encourage all our users to share their thoughts with us so we can continue to improve our services. Thanks for sharing!

## Janice · 1 year, 2 months ago

this is not useful, stop deleting my comments. freedom of speech.

## Janice · 1 year, 2 months ago

making the easiest sig fig complicated. not very useful, does whoever created it think they are so smart?

## Jwala · 1 year, 4 months ago

According to this we have to sail until we hit a non zero number when the zero is absent for example in 200 have 1 significant figure ,but in 002 we have just 1 sig fig ,but if we find sig figs by this method we will get 3 sig fig and thus my answer is not matching . Why this is so and what will be its true answer?? PLEASE HELP!!!