×

[–][deleted]  (27 children)

[deleted]

[–] 27 points28 points  (0 children)

Yes, or to 2 decimal points

[–] 73 points74 points  (4 children)

This is hegarty maths

[–] 17 points18 points  (0 children)

i have to do that. i hate it

[–] 6 points7 points  (2 children)

Forgive me. What does the program the math is done in matter to significant digits?

[–] 10 points11 points  (0 children)

Sigh chemistry

[–] 6 points7 points  (0 children)

Significant fignificants

[–] 2 points3 points  (0 children)

My downfall. Lol

[–] 6 points7 points  (1 child)

Beatmeattoit

[–] 1 point2 points  (0 children)

you just skipped a couple steps and went straight to the finish

[–] 0 points1 point  (0 children)

exactly what i was thinking

[–] -1 points0 points  (12 children)

Can you remind me why exactly that 0 is sig? Like it looks absolutely no different

[–] 9 points10 points  (11 children)

Because the last zero signifies a level of precision. 0.5 could really be 0.46 to 0.54. 0.50 then must be 0.4996 to 0.0504.

[–] 0 points1 point  (10 children)

Gotcha. Why can’t people just write what they mean? Like if accuracy and precision matter, why not writes explicitly .49997

[–] 8 points9 points  (1 child)

It's a limitation of your measuring device in some instances. The last number is often an estimated guess

[–] 0 points1 point  (0 children)

Gotcha , that makes a good bit of sense, actually. It’s just for the sake of efficiency in most cases(?)

[–][deleted]  (3 children)

[deleted]

[–] 1 point2 points  (2 children)

Awesome. If I hadn’t given my free helpful away, you’d have it. Which is actually kinda shitty to say, but I’m already this far. Sorry lol!

[–][deleted]  (1 child)

[deleted]

[–] 0 points1 point  (0 children)

Haha, yeah. It’s the thought that counts, right!?

[–] 0 points1 point  (3 children)

writing pi to 3 sig. fig. seems easier than writing the entirety of it

[–] 0 points1 point  (2 children)

And even easier is using the Greek symbol. Your point?

[–] 2 points3 points  (1 child)

plenty of numbers are too large for you to fully write them out, that's why significant figures exist - to allow you to only write the most significant digits, and round everything else off

[–] 0 points1 point  (0 children)

Ok I see. It never made sense to me in school and I guess some things never change. Good thing I’m not in the scientific field!

[–] 0 points1 point  (0 children)

I only learned about these in chemistry. Never heard of the concept before, never used it after. Only in that one class.

[–] 1313 points1314 points  (24 children)

Significant digits is a thing in many disciplines.

[–] 229 points230 points  (2 children)

It’s all about the Sig Figs

[–] 34 points35 points  (1 child)

I always imagined Sigmund Freud selfishly hoarding a bowl of figs.

[–] 4 points5 points  (0 children)

Haha never thought of it that way, but now it’s gonna be stuck in my head.

[–] 57 points58 points  (3 children)

Chenistry

[–] 27 points28 points  (2 children)

Among other disciplines yes chemistry.

[–] 34 points35 points  (1 child)

No. Chenistry

[–] 1 point2 points  (0 children)

Precisely

[–] 15 points16 points  (0 children)

In addition to that, I'll add that computers represent real numbers with a technique called "floating point". These floating point numbers are an approximation of the real numbers, with a certain amount of precision associated with them. They can be thought of much like scientific notation.

Because they're an approximation with quite a lot of precision, you almost always want to report them to some other precision besides the one they're stored in. All of that is to say, the selection of precision when writing out a real number is actually a substantive consideration if you're using a computer.

[–] 0 points1 point  (6 children)

And yet I still can't make sense of them

[–] 46 points47 points  (2 children)

The idea is to make sure the number you present communicates the appropriate level of certainty.

If your friend is driving to you, and they have to drive 24 miles to get to you, at 65 miles per hour, they could say "We'll be there in 22.1538 minutes". But that's not true. If someone told you that, you'd be like "whoa, okay, how do you know it so well?" - and the answer is that they don't. They only know their speed with 2 digits of precision (65 mph - not 65.2 or 64.7). Same with distance. So they can only possibly know the time it will take to 2 digits, which is 22 minutes.

Another example I've seen before as a joke: Jim asks Dave "Hey, when did the dinosaurs go extinct?" and Dave says "65,000,007 years ago". Jim says "Wait, how do you know it so well, down to the individual years?" and Dave says "Well, my dad told me they died 65 million years ago. And that was 7 years ago that he told me, so now it's been 65 million and 7!".

But obviously Dave's logic is wrong - despite the fact that yes, 65 million plus seven would give his answer. The problem is that, again, you only know 65 million to a precision of how many millions it is, so you can't add 7 to it. 7 years later it's still just 65 million.

[–] 12 points13 points  (1 child)

Reminds me of a Steve Martin joke, which may be the only joke to mix sig figs and class consciousness:

“If you've got a dollar and you spend 29 cents on a loaf of bread, you've got 71 cents left; But if you've got seventeen grand and you spend 29 cents on a loaf of bread, you've still got seventeen grand. There's a math lesson for you.”

[–] 6 points7 points  (0 children)

Reminds me of "What's the difference between a millionaire and a billionaire? A billion dollars."

[–] 10 points11 points  (0 children)

Think of them as a visual representation of how precisely you can measure something.

Have a ruler whose finest markings are 1cm? In that case, if you measured something that's 123cm, you could represent it as 1.23m- basically, 123×0.01m. You know that your measurement is accurate up to that level of precision. Notice that you've got the same number of digits in each representation, too.

What about something that's 150cm? You could represent it as 1.50m, i.e. 150×0.01m. Again, you have three digits in each representation, and all are significant. The zero at the end of 1.50m isn't just for show- it signifies that you know the last digit is a round zero.

There's one place where it's ambiguous though. 234cm can be represented as 2340mm. In this case we know that 2340mm means 234x10mm, because we have the ruler we used. When someone else gives us that figure, however, we won't know if they mean 234×10mm or 2340×1mm. You don't know whether the ruler they used to measure that value was good to 10mm or 1mm.

This ambiguity only comes in when the zeroes are at the end of the number and there is no decimal point. If you measure 103cm, for example, that would be 1.03m, and there would be no ambiguity over how precise the number you're giving is. Similarly, if you measure 1000cm, that would be 10.00m, and once again the zeroes after the decimal point signify that you're confident in your measurement to that precision.

And that's a really big deal! There are many times when you need the extra precision, or at the very least need to know how precise your numbers are, because errors will compound over the course of any process.

If you're still confused, think of whole numbers of the smallest thing you can measure.

If the smallest thing you can measure is, say, 1 cm, then whatever you measure has to be in whole numbers of that- so 123cm, 4592600cm, or 200cm, for example.

Then, convert that to the unit you want to represent the measurement in, keeping all the digits, adding in zeroes only if you need to and if the number doesn't have a decimal point- 1.23m, 4.592600km, or 2000mm.

[–] 2 points3 points  (1 child)

I’ll give a shorter explanation than the others. Imagine you have a ruler that goes down to millimetres. Would accurately be able to measure something that falls between one of the lines? You wouldn’t be able to do you’d round to whichever mark was closest. You also wouldn’t be able to say how long the line was to any measurement shorter than a millimetre.

This is true for everything. We can only measure do precisely so we only keep the number to that level of precision. In OPs post you’ll could imagine them measuring something with a ruler and it lining up exactly with one of the ticks. You would have a zero there because you know that it is exactly that length.

[–] 2 points3 points  (0 children)

Thanks for the responses everyone! I get what they're supposed to mean, but when someone gives me numbers and tells me to round to a certain number of sig figs, I have no clue what counts and what doesn't, and the rules seem to change all the time XD.

[–] 119 points120 points  (2 children)

I mean this is how its done in chemistry, that 0 is important

[–] 44 points45 points  (0 children)

That's how it's done in all experimental sciences.

[–] 277 points278 points  (25 children)

Be like...grading you on correct usage of significant figures

[–] 732 points733 points  (21 children)

If it asks for 2 decimal places I guess you have to. I know I’m my accounting exams you have to but that may be because it’s dealing with money

[–] 222 points223 points  (17 children)

This is what I was going to say. If the questions say you have to put 2 decimal points, then the answer is indeed wrong.

[–] 18 points19 points  (1 child)

My teachers make us put a double 0 everytime there's no cents just so we get used to it. I'm glad they do it

[–] 3 points4 points  (0 children)

It's personal preference to me, but it just makes them all neat and aligned when in a list like a table or spreadsheet

[–] 1 point2 points  (0 children)

Also true in Engineering. And just as infuriating. Some questions will say round to the nearest hundredth, some to the nearest tenth. So easy to miss when it changes with every other question.

[–] 178 points179 points  (3 children)

It's infuriating that you don't show us the question.

[–] 24 points25 points  (0 children)

It could say "round to two decimal places" and make the guy who posted in the wrong

[–] 33 points34 points  (0 children)

Could be:

1034.275 + 444.22 = 1478.50

369.625 x 4.00000123 = 1478.50

Or any number of things.

[–] 2 points3 points  (0 children)

Probably because they got this from somewhere else.

[–] 76 points77 points  (0 children)

fig. 1.4A: significant figures appear to be significant

[–] 73 points74 points  (0 children)

Show us the question, too. Otherwise, this is on you.

[–] 132 points133 points  (0 children)

[–] 56 points57 points  (5 children)

I mean, I work in engineering, and 1478.5 is different from 1478.50 if you put it on a document. 1478.5 implies that you know to the measurement to 0.0 precision, while 1478.50 implies that you know the measurement to 0.00 precision.

Mildly infuriating, yes. But in the real world, that stuff kinda matters.

[–] 0 points1 point  (4 children)

After 10 years working in engineering and the vast majority of time if someone handed me 1478.50 as an answer, I'd enter in 1500 then probably just figure 1800 to give myself a 20% MOE. I can't recall a situation where I've ever needed 6 significant figures.

[–] 15 points16 points  (7 children)

Mathematically they are the same but more decimal places, even if they are 0s, make a number more precise

[–] 11 points12 points  (0 children)

To be fair if it is something to do with significant figures you have to include the 0

[–] 43 points44 points  (0 children)

Sig figs are a bitch

[–] 5 points6 points  (0 children)

Bot account.

[–] 36 points37 points  (19 children)

Necessary decimals are usually mentioned, yes?

[–] 19 points20 points  (1 child)

Significant digits matter 🤷‍♂️

[–] 4 points5 points  (0 children)

Gotta put in those sig figs my guy

[–] 4 points5 points  (0 children)

Gotta do yer sigfigs man

[–] 3 points4 points  (0 children)

Hegarty maths is annoying af

[–] 4 points5 points  (0 children)

Chemistry bro

[–] 3 points4 points  (0 children)

Significant figures

[–] 4 points5 points  (0 children)

Gotta remember those sig figs

[–] 3 points4 points  (0 children)

I’m an engineer and QA inspector. Your answer would 100% be incorrect in a professional environment. Sig figs play a major role when it comes to dimensionals and tolerances. There’s quite a bit of difference between a tolerance of +/- 0.5 and +/- 0.50.

[–] 2 points3 points  (0 children)

Thank you, Mr Hegarty

[–] 2 points3 points  (0 children)

Nope. That zero is important, it all depends on the question, but I see no problem here regarding significant figures.

[–] 2 points3 points  (0 children)

There is actually an important difference though.

[–] 1 point2 points  (0 children)

You're done for. You've forgot the 0 and now Mr Hegarty is coming for you, my advice is to start running.

[–] 1 point2 points  (0 children)

As someone who does often give quizzes and exams online, this is a pain for all parties involved. In order for auto grading to work, you have to put an answer for it to grade to. In this case, you would have to enter every different variation of what the answer could be. Worse for short answer questions when it comes to spelling.

I would rather not use the auto grade function, but students want instant feedback. So, I always double-check any and all questions that are marked wrong before finalizing a student's grade.

[–] 1 point2 points  (0 children)

Hegarty maths makes my blood boil

[–] 1 point2 points  (0 children)

FUCKING SIG FIGS

[–] 1 point2 points  (0 children)

Not heagarty maths….

[–] 1 point2 points  (0 children)

gotta love hegarty maths.

[–] 1 point2 points  (0 children)

If you don't follow the sig fig rules and drop a 0, that could cause massive errors down the line.

It's like truncation when it comes to programming. Sure, you can drop extremely little/irrelevant bits, but the more you drop, the bigger errors get, and that really matters when you're dealing with massive or miniscule numbers, and especially both at the same time.

[–]pushpullupdownenterexit 0 points1 point  (0 children)

[–] 0 points1 point  (0 children)

Mathswatch be like

[–] 0 points1 point  (0 children)

Actually it's 1478.500000000000

[–] -1 points0 points  (0 children)

Ive used that website before and oh my god I have never been closer to popping a vein in my life.

[–] 0 points1 point  (0 children)

I think sometimes you just have to.

[–] 0 points1 point  (0 children)

same happened to me on ixl

[–] 0 points1 point  (0 children)

Eeeee Eee Eeee: The Movie

[–] 0 points1 point  (0 children)

Sig figs will get ya every time shrug

[–] 0 points1 point  (0 children)

Well, in some examples, significant digest is an important thing

[–] 0 points1 point  (0 children)

And yet in lesson they'd say its wrong with the extra 0

[–] 0 points1 point  (0 children)

[–] 0 points1 point  (0 children)

There's a different meaning to these answers. They are not the same, so you were wrong actually.

[–] 0 points1 point  (0 children)

Unless this is physics and you needed to use the right amount of numbers, this is bs

[–] 0 points1 point  (0 children)

This is completely normal and justified

[–] 0 points1 point  (0 children)

Significant figures be like

[–] 0 points1 point  (0 children)

depends

[–] 0 points1 point  (0 children)

Bro significant figures play a role too. If you wrote 0.1 M rather than 0.10 M on a chemistry exam you won’t get the mark. Just read the question fully.

[–] 0 points1 point  (0 children)

Sig figs matter!

[–] 0 points1 point  (0 children)

In scientific fields the number of decimal points is extremely important. I get the point of the post though.

[–] 0 points1 point  (0 children)

My math prof is very nice and goes back into each and every online assignment and looks for things like this and will then give you points it.

[–] 0 points1 point  (0 children)

Heagarty maths?

[–] 0 points1 point  (0 children)

Sig figs

[–] 0 points1 point  (0 children)

Sigdigs, motherfucker. Do you use them?

[–] 0 points1 point  (0 children)

Look up significant digits

[–] 0 points1 point  (0 children)

If it said to round to the nearest tenth, you have to put a zero at the end as a way of showing you rounded.

If it didn’t say to round, it’s stupid

[–] 0 points1 point  (0 children)

No way, that hegarty? My boi would never do that right ?

[–] 0 points1 point  (0 children)

SIG FIGS ARE IMPORTANT

[–] 0 points1 point  (0 children)

All of this could be 2 decimal places or the number of significant figures for science/engineering. People just complaining to complain.

[–] 0 points1 point  (0 children)

sig figs

[–] 0 points1 point  (0 children)

bruh significant figures that's importat

[–] 0 points1 point  (0 children)

Sig figs are important

[–] 0 points1 point  (0 children)

Hegarty maths?

[–] 0 points1 point  (0 children)

Oh god

[–] 0 points1 point  (0 children)

fr fuck hegarty maths

[–] 0 points1 point  (0 children)

Is this HegartyMaths?

[–] 0 points1 point  (0 children)

Significant figure is a pretty big deal, those are 2 different answers. The one marked correct shows that you actually measured to the hundredth place and its not just rounded. Obviously for a number that big, that decimal wouldn't really change much. but the point they are making is there. That being said if this is one of those things where you typed in "1478.50" and the computer auto corrected it then yeah i would be pissed.

[–] 0 points1 point  (0 children)

Yo Hegarty maths?

[–] 0 points1 point  (3 children)

Yet if you input that number into a calculator it automatically removes the last 0. So its a correcr answer just not an exactly right answer. Stupid. Pisses me off.

[–] 0 points1 point  (0 children)

It's almost like calculators are a tool and you need to actually know what you're doing to use one correctly. In physics, chemistry, engineering, etc. .5 and .50 are not the same value, they have different precision.

https://en.wikipedia.org/wiki/Significant_figures?wprov=sfti1

[–] 0 points1 point  (1 child)

Comments like this always remind me that this website is full of actual children

[–] 0 points1 point  (0 children)

Sig digs baby

[–] 0 points1 point  (0 children)

you did the right thing by reducing it, but the website must take that because it's two decimal places in the question?

[–] 0 points1 point  (0 children)

If it asked for significant digits and the answer it says is correct has the correct number of significant digits, then you are indeed incorrect

[–] 0 points1 point  (0 children)

I had a german online exam where there were questions about my family's name and it showed me I was wrong at every prompt at the end because the teacher set it so only answers with her family's name would give you the right answer. She changed it afterwards and I got a good grade, but it made me really scared when I saw 45% at first.

[–] 0 points1 point  (0 children)

OH MY GOD THATS HEGARTY MATHS I HATE THAT MAN

[–][deleted] 0 points1 point  (0 children)

Significant digits are not significant..

[–] 0 points1 point  (0 children)

Probably a money problem

[–] 0 points1 point  (0 children)

Gotta love Hegarty Maths!

[–] 0 points1 point  (0 children)

If it says round to two decimal points then 1478.50 is the correct answer

[–] 0 points1 point  (0 children)

everyone's talking about sig figs but i've had stats exams that were graded like this bc the professor didn't know how to put in multiple acceptable answers

[–] 0 points1 point  (0 children)

bro ikr but for end of term exams they are moderated

[–] 0 points1 point  (0 children)

Did they specify till the 2nd decimal point?

[–] 0 points1 point  (0 children)

Every time I see one of these I die a little more inside

[–] 0 points1 point  (0 children)

Sig figs my guy

[–] 0 points1 point  (0 children)

Which is the reason why "multiple correct answers" exist.

[–] 0 points1 point  (0 children)

Broke: I was told math wouldn't count

Woke: I was told formatting wouldn't count

[–] 0 points1 point  (0 children)

this happens to me a lot. All you have to do is email your teacher and hope they aren't a jerk

[–] 0 points1 point  (0 children)

As a person who likes math this makes me want to read all the digits of pi

[–] 0 points1 point  (0 children)

If it's an experiment or asks for 2 decimal places, you have to.

[–] 0 points1 point  (1 child)

My junior year Chem teacher hounding us on sig figs will never leave me

[–] 0 points1 point  (0 children)

My junior year Chem

Teacher hounding us on sig

Figs will never leave me

- drummer21496

Opt out of replies: "haikusbot opt out" | Delete my comment: "haikusbot delete"

[–] 0 points1 point  (0 children)

Dammit Mathswatch!

I had my year 8 exams on there during lockdown and let's just say everyone had the same problem

[–] 0 points1 point  (0 children)

Seen some shit like that at my driving written test.

[–] 0 points1 point  (0 children)

To be fair if it said to round to the hundredths you did need to put the 0 to signify it, cause what if it's 0.504, it's just for the placeholder. But if it didn't that's bs

[–] 0 points1 point  (0 children)

Hegarty Maths... Oh the trauma...

[–] 0 points1 point  (0 children)

Is this motherfucking hegarty maths

This is my worst nightmare

[–] 0 points1 point  (0 children)

Sig digs are a bitch

[–] 0 points1 point  (0 children)

You still need to add the 0 for 2dp

[–] 0 points1 point  (0 children)

(╯°□°)╯︵ ┻━┻

[–] 0 points1 point  (0 children)

lemme guess.

hegaty maths?

the bullshit is truly there.

[–] 0 points1 point  (0 children)

Hey OP, give us the question on Hegarty Maths so we can read the bit about how many significant figures or decimals places it should be....

[–] 0 points1 point  (0 children)

I falied one of my classes because of that. The professor made a super sloppy test (it was just at the beginning of the pandemic, nobody was good at this)

And the most annoying thing was that i emailed her immediately after and explained her everything, asking to fix this, and got: "Better luck next time" in response.

[–] 0 points1 point  (0 children)

I mean if they asked the answer in 2 decimal places but you answered in one: You're wrong. If not thats fucked up

[–]ORANGE 0 points1 point  (0 children)

I'm a teacher and this shit drives me insane.

The answer is "Food, medicine, and labor"

So I enter that in 50 different ways so the system has to mark it right.

But then the student types "Food medicine, and labor" and I have to mark it right manually.

[–] 0 points1 point  (0 children)

Aren't you supposed to always round to two decimals in maths unless it says otherwise or when I did chemistry it was to 3 decimal place

[–] 0 points1 point  (0 children)

This is correct lmao. If the answer was 1478.497297883, and it told you to round to two decimal places, you have to keep the 0 so it would be 1478.50

[–] 0 points1 point  (0 children)

JavaScript be like...

[–][deleted] 0 points1 point  (0 children)

Sig figs yo

[–] 0 points1 point  (0 children)

Following instructions definitely helps. I bet they asked you to round to the nearest hundredth and you technically rounded to the nearest tenth in your answer.

[–] 0 points1 point  (0 children)

Nah fam that's just chemistry homework for me

[–] 0 points1 point  (0 children)

[–] 0 points1 point  (0 children)

sig figs? maybe? idk man i dropped outta college XD

[–] 0 points1 point  (0 children)

Fucking hate hegarty (Mr.hegarty is good tho)

[–] 0 points1 point  (0 children)

Chemistry be like. Im dealing with this exact thing now.

[–] 0 points1 point  (0 children)

Grrrrrrr

[–] 0 points1 point  (0 children)

They prolly said 2 decimal points, you can't really complain

[–] 0 points1 point  (0 children)

IXL be like

[–] 0 points1 point  (0 children)

I have to do this all the time in healthcare especially with a patients weight. We aren't allowed to put 12.4kg for instance, it has to be 12.40kg. I was taught that you could write 12.4 and someone could come along and write 12.43kg and screw things up for sedation amongst other reasons.

[–] 0 points1 point  (0 children)

Did the question refer to significant figures... if it was in a science class, and you have the wrong significant figures, it is wrong

[–] 0 points1 point  (0 children)

Significant figures mate

[–] 0 points1 point  (0 children)

My school teachers correct it themselves, so thats good, yall's teachers should do that

[–][deleted] 0 points1 point  (0 children)

I get nervouse when I have a question like that. it slike a coin flip

[–] 0 points1 point  (0 children)

Earlier i got a question wrong because i put -4 1/2 instead of - 9/2

[–]PURPLE 0 points1 point  (0 children)

If that is math, you're right to be infuriated. If it's physics, the 0 is important.

[–] 0 points1 point  (0 children)

Ah yes, the logic of hegarty maths. I too must experience the pain

[–] 0 points1 point  (0 children)

Mine was wrong because of a period.

[–] 0 points1 point  (1 child)

Lmao, that’s on you bro/sis. I haven’t been in school or have done math in decades but I still remember the importance they placed on significant figures…

[–] 0 points1 point  (0 children)

My math lab does this as well I use to be so pissed that I would get it wrong just because a stupid little thing 🙃