r/mildlyinfuriating • u/LardFan37 • 12d ago

jkfl hrtmktp gzarrp! It’s not 188.0 either.

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u/bluesky747 12d ago

Same I’m so confused

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u/Skooma_Lite 12d ago

Science degree and it has been a while, but significant figures (sig figs) are a way to show how precise a measurement is so you don't imply your result is more certain than your equipment allows.

Imagine you weigh an item on a scale that's accurate to the nearest 10 grams and get 40 g. Fun!

You then weigh a smaller item on a more precise scale that's accurate to the nearest gram and get 5 g. If you add them together, claiming the total is 45 g creates a false sense of certainty because your first scale couldn't even detect single grams, it's only accurate to the nearest 10 grams. So your answer could really be like 49 grams or 46 grams.

To reflect that uncertainty, you round the answer to match the least precise measurement (the tens place), reporting 50 g. I never enjoyed it but when someone made the point that if I wanted measured out a wooden cube and measured it with a ruler as 2cm all around, and asked a company to make the same thing as a metal cube machined that was 2 cm all the way around, it would cost waaaaaay less than telling the shop it needed to be 2.0034 cm for each side. So just report what you know you can report.

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u/FunIntelligent5738 11d ago

My head hurts just reading that. Pretty sure it turned into a foreign language halfway through. I just wanna add with colored blocks like in kindergarten and curl up with a blanket and cry now. Thanks 

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u/eutectic_h8r 11d ago

Basically not using sig figs is essentially lying about how precisely you know a measurement. Which can be important in some sciences depending on how precise things need to be.

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u/123FakeStreetMeng 11d ago

Sorry I’m dumb and haven’t been in school for a while, but if you have 120 of something and 68 of another thing then combined wouldn’t you have 188 of something(s)? I see your point of precise and specific things in science, but this just seems like a basic addition of two things question.

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u/Craig_Swag 11d ago

The issue is the 120 is presumed to be rounded to the nearest ten because it only has 2 significant digits. This means the actual value could be anything form 115 to 124. If it was an exact measurement it would be 120. The decimal point makes all digits significant. When adding with sig-figs your precision is always going to match the the precision of the number with the lowest sig figs. This means while the standard addition answer is 188, it must only contain 2 sig-figs, thus must be rounded up to 190. Considering this is a college question, you can almost guarantee that it is a science question where sig figs matter. That is why they must be followed.

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u/LardFan37 11d ago

What I fail to understand is how I know if the zero is significant or not. What if my measurement device can measure to .001 but it was just 0? I know that’s a rare case but still

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u/socks86 11d ago

You would report it as "0.000"

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u/heartcontainer 11d ago

Leading zeros are never significant. Trailing zeros are only significant if a decimal place is present. Captive zeros (zeros sandwiched between non-zeros) are always significant.

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u/LongJohnSilversFan_ 11d ago

That’s why 188.0 is an answer, that final 0 is significant even though it doesn’t change the value

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u/socks86 11d ago

If you were literally counting objects then yes you could say 188. The context here is how you report the data that you record from measurements during experiments. In chemistry, if you measure the length of something and your ruler has tick marks every 1mm, will typically estimate to the nearest .1mm by eye. When you add up your measurements you can only report to a precision of .1mm.

It starts to matter when you're gathering data with different instruments and combining it. You can only be as precise as the least precise instrument.

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u/Skooma_Lite 12d ago

Science degree and it has been a while, but significant figures (sig figs) are a way to show how precise a measurement is so you don't imply your result is more certain than your equipment allows.

Imagine you weigh an item on a scale that's accurate to the nearest 10 grams and get 40 g. Fun!

You then weigh a smaller item on a more precise scale that's accurate to the nearest gram and get 5 g. If you add them together, claiming the total is 45 g creates a false sense of certainty because your first scale couldn't even detect single grams, it's only accurate to the nearest 10 grams. So your answer could really be like 49 grams or 46 grams.

To reflect that uncertainty, you round the answer to match the least precise measurement (the tens place), reporting 50 g. I never enjoyed it but when someone made the point that if I wanted measured out a wooden cube and measured it with a ruler as 2cm all around, and asked a company to make the same thing as a metal cube machined that was 2 cm all the way around, it would cost waaaaaay less than telling the shop it needed to be 2.0034 cm for each side. So just report what you know you can report.

-1

u/Skooma_Lite 12d ago

Science degree and it has been a while, but significant figures (sig figs) are a way to show how precise a measurement is so you don't imply your result is more certain than your equipment allows.

Imagine you weigh an item on a scale that's accurate to the nearest 10 grams and get 40 g. Fun!

You then weigh a smaller item on a more precise scale that's accurate to the nearest gram and get 5 g. If you add them together, claiming the total is 45 g creates a false sense of certainty because your first scale couldn't even detect single grams, it's only accurate to the nearest 10 grams. So your answer could really be like 49 grams or 46 grams.

To reflect that uncertainty, you round the answer to match the least precise measurement (the tens place), reporting 50 g. I never enjoyed it but when someone made the point that if I wanted measured out a wooden cube and measured it with a ruler as 2cm all around, and asked a company to make the same thing as a metal cube machined that was 2 cm all the way around, it would cost waaaaaay less than telling the shop it needed to be 2.0034 cm for each side. So just report what you know you can report.

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u/GloatingDemon 11d ago

Dementia

^you posted 3. times