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# How can 590+ solvers miss this?

Update: The problem as stated is correct. We have removed erroneous solutions.

First I do not intend to offend or criticise any individuals here. Everyone makes mistakes; I certainly do make a lot of them. Having said that; I am somewhat surprised and disillusioned by the total acceptance by brilliant.org and the 591 solvers of the problem Va is the same at all branch.

This question clearly poses and impossible scenario that could never possibly happen. Current, voltage and resistance values within any circuit are always related by the relationship I=V/R. We cannot arbitrarily assign values to each these (I,R,V) and then actually make a circuit that fulfills all the criteria as given. We can only assign a value to any two of the criteria and the third value will be dictated and can be calculated.

In the problem it appears that the given values for the resistors the battery voltage and the current at the meter where each set independent to the others producing a nonsense scenario.

If that kind of problem is considered valid then how about a question like this one?

A train moving at a fixed speed of 1 mile per hour, travel between two points on a track that are 1 mile apart, and the trip take 3.5 hrs what is the time at the half way point? Clearly this question is not valid, it cannot happen, something must be changed to make sense of it. There are no meaningful answers to either of these questions. Each individual solver will have to ignore or alter some bit of the information given to make any sense of the scenario.

For me the nonsense problem is of little interest it is just a mistake. The fact that 593 solvers tried the problem, 32% of the solvers arrived at the same answer and 11 posted solutions is very interesting. How is this possible? How can so many people attempt a problem like this and not see that it is not valid?

A couple of days ago, I posted a dispute where I pointing out that this problem is not valid. I have seen no reply or explanation from brilliant.org or anyone else. I find it disappointing. Is this possibly an indication of the general validity and quality of the sites problems and answers?

I would be interested in comments as to how this question has survived this long. What are the solvers thinking? Perhaps the reality was they where not doing much thinking at all. Does anyone care?

Note by Darryl Dennis
2 years, 10 months ago

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Thanks for bringing this problem to our attention. We do our best to catch all the mistakes, and this one slipped through the cracks. I will update this thread once I have fixed this problem.

At Brilliant, we receive a ton of problem submissions from many different people. Unfortunately, I do not have the ability to personally review every single problem that comes in. I do my best to ensure that problems are correct, but I'm only human. As such, we rely on the community to help us report the problem when they feel that something is wrong. We then give the problem creator 2 days to respond, after which we will look into the problem and try our best to figure out what the best approach to resolving the problem is.

The problem that you are referring to is V_a is the same for all branch. In this case, you were the only one that reported it, and we have yet to get to your report. There had been no other reports which alerted our attention to it. I see now that there are comments which disagree with the various solutions, but as we are unable to review every single comment that come in, we do still rely on reporting as the main way of indicating that a problem is incorrect.

The issue of "This question clearly poses and impossible scenario that could never possibly happen." is not as rare as you would think. If the problem creator made a mistake but had an answer that could be arrived at in many wrong ways, people who make the same mistake would then use those wrong ways to arrive at the "correct" answer. After which, they would think that they were validated by their approach, and proceed to type up their solution. This happens more often in Geometry, where the described geometrical figure can never occur, but the sequence of steps lead to some numerical solution (e.g. requires $$\sin \theta = 1.5$$, or has an overdescribed geometric figure). We do a pretty good job of removing these problems as they appear, which is why you have not seen them. Often, they also lead to my posing of questions of the form "Inspired by XXX", which highlights the mistake that was made. For example, see this and this.

It does take a certain finesse to properly set a good and interesting question. As contributors of problems, members of Brilliant are working on improving our skill of doing so. It will take time for an individual to master the skill, and those who have began that process have learnt much from the comments and reports that they have received. I encourage everyone to help the problem creators learn, by explaining how they can improve their problems.

Staff - 2 years, 10 months ago

Hello sir.I had a small query.can u please tell me how to report the errors if found in problems posted by other brilliant users using the brilliant mobile app. As far as i have checked it,there seems to be no such option sir.if there is any,plz do reply.and also can u plz make it possible to add links in the comments or solutions so that the solvers can provide necessary reference for new concepts implemented in the problems.sometimes solution alone won't be sufficing.thank u.

- 2 years, 10 months ago

It's the same process as on the desktop

On the problem, click on the "dot dot dot" / "More" menu, and you will see "Report Problem".
Android app view:

Staff - 2 years, 10 months ago

I just find it Interesting, how a such a large number of independent solvers can be satisfied with a problem and answer that is so clearly flawed. ;)

- 2 years, 10 months ago

It is not an uncommon scenario, especially if the problem creator is disengaged with the problem. It further slips through the cracks when there are multiple solutions submitted since people then think "10 solutions cannot be wrong". or "If it's wrong, someone else would already have reported it, so I guess my logic is somehow wrong". As such, we rely on people like you to help us identify the issues, so that we can work on fixing them.

In part, I blame the education system for ingraining "THIS is the correct answer. OBEY me unconditionally". I try and counter that when I see it, and encourage people to think for themselves (like in this case). Often, you can see me comment in solutions saying "Can you explain why that is the only answer", especially when the solution is of the form "I tried 5 and you told me I was correct, so the answer is 5." or "If we make this (baseless) assumption, the answer is clearly 5.".

Over time, I've seen members develop their own sensibilities, and they become more confident in reporting problems that are wrong. Of course, not all reports are valid, and we are all in a huge learning pool.

Staff - 2 years, 10 months ago

Thanks for reply. It is somewhat understandable as you explain it, but very much unexpected that it would happen to this extent , almost 600 solvers.

All is well in the brilliant.org world. There is a vertualy unlimited variity of problems to think about here. I can't imaging trying to keep track of them all.

Have a great day

- 2 years, 10 months ago

What's more interesting is that you have found out an error that many had previously failed to notice :) Have you posted a dispute to the problem sir ?

- 2 years, 10 months ago

We looked over the problem, and we find that it is alright. There have been several erroneous solutions, and we have removed them. The top solutions are correct.

To help clear up your misunderstanding: it seems that you are under the impression that the current source is an ammeter, but it's not a measuring device, it's an actual current source. Look at circuit superposition or to transform the current source into a battery which can be done by using Ohm's law with the current of the source, along with the resistance it is in series with (here that is 2 Ohms because it's in series with a 1 Ohm and a parallel circuit with effective resistance of 1 Ohm). By Doing superposition, you get that the battery and the current source give rise to opposing currents in the 2 Ohm that's directly connected to the battery so that there's actually no current flowing down it.

Staff - 2 years, 10 months ago

Ohhhhhhh. This certainly explains the trouble I was having with what seemed to be a rather simple question. I was under the impression that that thingy was an ammeter and not a current source. Thanks a lot for clearing up the misunderstanding!

- 2 years, 7 months ago

I am sorry for all the fuss I started.

I was not familiar with the symbol for a constant current source. I like the solution now that I understand the question. This makes a lot more sense to me then 590 solvers missing something so basic. I looked at that problem so many time trying to figure out where I was misreading things, it just did not occur to me to look up the symbol definition for the 1 amp component. It looked like a ammeter to me..

If I ever have another dispute or something I need clarified I will just post it on the problem dispute area and wait longer for an explanation from that post.

- 2 years, 10 months ago

Thanks for helping us keep Brilliant problems problem-free. (I just couldn't resist that wordplay. I'm sure you know what I mean.)

I certainly understand that not all reports are valid, and sometimes we just need to clear up our concepts, especially with things that we've not seen in the past.

Staff - 2 years, 10 months ago

As Calvin points out, it's pretty difficult to review and check out all the problems being posted on Brilliant. I try to do my part, but sometimes I feel like I'm having to fight a forest fire armed with a water pistol. But Brilliant has already come a long way in greatly improving the quality and accuracy of the problems on Brilliant, I highly commend the results of the efforts of the Brilliant staff and its small army of moderators.

I agree with the points raised by Calvin. Maybe there is a kind of a herd mentality in the way some people approach problems, so they automatically assume what is being asked of them, and so they respond by rote--even though the problem maybe be poorly or ambiguously stated, and the answer even incorrect. I've run into this before on Brilliant. But, trust me, it's been getting better and better. Reports and comments by Brilliant users such as you helps--they are being taken seriously.

- 2 years, 10 months ago

I totally agree with your last point sir , I've been here for only 84 days and I myself have experienced quite a few significant but Brilliant modifications , I can only imagine what all changes you would have seen !!

Have a nice day sir !

- 2 years, 10 months ago

Comment deleted Mar 05, 2015

That's weird... It didn't even said deleted.

- 2 years, 10 months ago

I guess it'll be best if Calvin sir deals with this . Btw are you a moderator ?

- 2 years, 10 months ago

Nope.

- 2 years, 10 months ago

Can you please provide the link to the question since I am not able to find the question . Also I am inviting Calvin sir to this discussion since he might be in a better position to resolve your doubt .

- 2 years, 10 months ago

I can't find it too. Maybe it has been deleted.

- 2 years, 10 months ago

I think so too .

Hey , can you give me some advice on how to make good questions ? All your questions turn out to be one of the best here on Brilliant !!

- 2 years, 10 months ago

Most of the questions I make are found unintentionally. Usually I find a "new thing" when I play with a graphing calculator (I use Desmos a lot) or solve problems on brilliant.

- 2 years, 10 months ago

Ok , I'll keep that in mind :) Even I'll start playing around with others questions !!

- 2 years, 10 months ago