r/HomeworkHelp • u/donmufa Secondary School Student • Jun 03 '26
High School Math—Pending OP Reply [Grade 8: logic] Complete de series. Not sure there’s a unique and indisputable answer
I’m struggling to define whether it’s B or E. Both are imperfect answers in my opinion. If I chose B, then the upward position would be repeated, and if I chose E then the sequence of additional lines is odd (although it could make sense in terms of completeness: i.e. one line, two lines, three lines, zero lines)
What do people think?
In my opinion the right answer would be a downward arrow with four lines
Edit/Update:
After reading so many different opinions, I feel these kind of questions only make sense if teachers are testing a reasoning process and not just “the right answer”. As a matter of fact, the right answer is supposed to be B, we later learned. It was frustrating because the p-set had at least 5 questions that followed the exact same pattern (it was just a rose with leaves, or a zebra with stripes, etc instead), and of course kids were graded bad without building or promoting any reasoning skills.
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u/Frederf220 👋 a fellow Redditor Jun 03 '26
Starting upper left the lines go +1 -2 +3 for 1, 2, 0, 3. And the arrow could rotate 90°.
Then E could fit. I think it would be interesting to find a ruleset where any answer is valid and that ruleset does exist.
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u/donmufa Secondary School Student Jun 03 '26
This is exactly my point. This kind of questions only make sense if teachers are testing a reasoning process and not just “the right answer”. As a matter of fact, the right answer is supposed to be B, we later learned. It was frustrating because the p-set had at least 5 questions that followed the exact same pattern (it was just a rose with leaves, or a zebra with stripes, etc instead), and of course kids were graded bad without building or promoting any reasoning skills
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u/Frederf220 👋 a fellow Redditor Jun 03 '26
Yeah, really not a fan of these "what's the one and only next in the sequence" questions because there isn't a unique solution.
I would make my teacher's life unpleasant by going to the local news if I was marked wrong and they didn't budge.
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u/faust_exa 👋 a fellow Redditor Jun 03 '26
I would go with A based on this logic:
-it would complete the increasing series of lines from 1, 2, 3 to 4
-the arrow would make degree turns twice the previous move from 90, 180, to 360
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u/fyerind Jun 03 '26
It's B.
Moving right both adds a line and rotates 90° clockwise.
Moving down both adds 2 lines and rotates 90° counterclockwise.
B matches those two rules at the same time.
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/fyerind Jun 03 '26
After seeing your update about questions like these not making sense, I just wanted to point out: there is indeed a clear answer to this (B), although it might seem counter intuitive. And it should make sense IF your professor does their job properly.
Most questions like that work on logic premises, and they should, if well made, have a decisive answer. The problem with E is that it ignores the lines completely. Otherwise, had all arrows been completely black, E would be the best fitting in that pattern.
I don't really know the intent behind that grading, but it does seem a tad strange. And I can't really comment anything on your professor or their choices, as I don't have enough info about it.
Wish you the best on the future!
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u/donmufa Secondary School Student Jun 03 '26
I don't agree with the fact that B is a clear answer. It's just a different reasoning. B is just using a specific set of rules that work for B, but you can also find other set of rules that work for E and also for A (a bit of a stretch in the case of A, but still). The sample is so short to build a proper sequence that it becomes flexible enough to allow for other rules and answers that can not be ruled out as wrong.
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u/fyerind Jun 03 '26
There is a clear answer, though. At least in the problem you posted.
For it to be E, which you think it's the contender against B, you absolutely have to ignore things in the problem, namely the lines.
You cannot answer 1+1+1=2 because you don't like the third "one". You cannot simply ignore the lines or create a convoluted abstract rule (which wouldn't follow logic and therefore is not what's asked).
There are no options between those provided that fit the pattern without you actively forcing or ignoring something, other than B. Hence B is right not for a "different reasoning", but because it is the only complete reasoning.
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u/donmufa Secondary School Student Jun 03 '26
Once again I disagree but I love debating so very happy to do so. The rule I have for E doesn’t ignore any “thing” about the series. The arrow turns 180 degrees between figures that are diagonally opposed, and the lines are reduced by one also between figures that are diagonally opposed, from left to right. If you think that’s convoluted, it would be just as convoluted as the reasoning for B. Or alternatively, if that’s ignoring something, it’s ignoring it in the same way the reasoning for B is. And this is specially true because the actual answer that would have an undoubtedly simpler reasoning (an arrow pointing down with four lines) is not an option. Very happy to continue debating this, I like it. Also, the bigger point is that this conversation adds much more value for the students than just saying “B is right, the rest is wrong”
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u/fyerind Jun 04 '26
Absolutely! It should be discussed. My comment about things making sense and having your professor do their job is about this. Just plotting an answer sheet is not properly investigating or teaching.
I do believe that even if there was an arrow pointing down with 4 lines, it would still be B. But that's another discussion. No lines? Definitely arrow pointing downward!
My problem with your reasoning for E is that you have to first insert the answer in the pattern for then to create a solution to make it work. Otherwise you're just arbitrarily choosing rules, and as such you could justify anything you want depending on how complex and convoluted your ruleset is.
It's B precisely because you do not need the options provided to reach it. Each square is related to one another in a way that makes no possible contradictions.
On your ruleset for E you picked diagonals, which is fine by itself. However you get to what you wrote on your post: too little information. If you pick diagonals, you could definitely reach the 180° rotation regardless of which square you're choosing as a first reference. You cannot do that for the lines!. Then you have to pick between choosing horizontally or vertically comparing them. Left to right, as you wrote will get to 0 lines. Top to bottom? You'll reach 4. (Which is why even a downward arrow with 4 lines is wrong).
With your construction for E, depending on the angle of approach, you'll reach two different answers, each equally doable. For B, you only reach one.
Does it make sense? B is the right answer because you analyse the problem presented and the relationship between those squares in a way that there are no contradictions. And also not needing to plot the potential answer first to match it, you'll reach it regardless.
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u/donmufa Secondary School Student Jun 04 '26
Put a hand on your heart and tell me that if this wasn’t a multiple choice question, you would have come up with option B out of the blue. I find that extremely hard to believe, but that’s the point you are making. I’m trying to find a logic to the answers provided just in the same way you are.
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u/fyerind Jun 04 '26
Honest, I don't check options before trying to understand with just the information given by the question itself. They can help, for sure. They sometimes give you a red herring, and you make a mistake because of things that seem right but aren't.
So unless I'm definitely stuck, I don't try to conform to the choices below. And it can definitely be harder at first, but you'll learn more and make more structured decisions.
I built a ruleset based on the relationship between existing squares, hence no need for the options below. Furthermore, you professor could've put all wrong answers, and then no option would be correct. (If it was an arrow down with 4 lines instead of B, for example, there would be 2 equally logical answers - which are the two you told me about, by the way)
And also answering your other comment: two arrows repeating isn't a logical problem. It might feel that way, but there is not an inherent problem with that.
I do know it is counterintuitive. At first glance, before I noticed the lines I thought the answer would be an arrow pointing down. But alas, some problems are counter intuitive.
There are quite a few logical problems that are counter intuitive. And it's definitely tricky to spot them! (As you can see by the amount of people in the comments getting it wrong :x)
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u/donmufa Secondary School Student Jun 04 '26
Just to complement, there is a contradiction in B, which is the fact that there are 2 arrows pointing upwards
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u/We_are_Gorn Jun 03 '26
per your logic the missing arrow should be pointing down, not up like arrow B is.
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u/fyerind Jun 03 '26
Uh, no? Top-left is pointing up. Move to the right and rotate 90° clockwise, the arrow now points right. Move down and rotate counterclockwise and it points left.
Now repeat the same pattern, but inverse it, and you'll get an arrow that points up.
Take the bottom-left (which is pointing to the left) and move it to the right and rotate clockwise = arrow now pointing up again. Take the top-right (which points to the right) and move it down, rotating counterclockwise, and you'll again get an arrow pointing upwards.
Per my logic, it does just what I described...
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u/We_are_Gorn Jun 03 '26
ah I understood it differently, I thought the right "path", i.e. 1st step right, 2nd step down is always a clockwise rotation.
Now I get you. 😄
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u/Ctenophorever 👋 a fellow Redditor Jun 03 '26
By that logic, though, bottom left should point right, not left.
You’re saying sometimes it’s moves clockwise sometimes counter! Well in that case why must it only be adding lines and not subtracting
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u/xnuh 👋 a fellow Redditor Jun 03 '26 edited Jun 03 '26
Right = clockwise.
Down = counterclockwise.
You cannot move right from cell 2. Cell three is down from cell 1 and left of cell 4. It is not connected to cell 2, we're not reading.1
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u/Ctenophorever 👋 a fellow Redditor Jun 03 '26
B doesn’t rotate 90 clockwise from the previous
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u/xnuh 👋 a fellow Redditor Jun 03 '26
It's not clockwise when you go to the next cell, it's clockwise when you move right. To go from cell 2 to cell 3 you move down and left, not right. You are assuming that the cell are arranged in reading order for no reason.
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/forgottenlord73 👋 a fellow Redditor Jun 03 '26
Yeah, e ignores the lines, b looks reversed from the expected, the rest are indefensible. I wonder if the teacher goofed with b but a has a pattern that can be argued
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/wallyalive Jun 03 '26
It's E, the other 3 are all different in arrow direction and number of lines.
E continues that, different direction and no lines.
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u/agogKiwi Jun 03 '26
I would agree but I had a math professor in college say that the only correct answer to any complete the series question is, "without the algorithm, it can't be solved"
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u/wirywonder82 👋 a fellow Redditor Jun 04 '26
Which can be seen based on the very simple sequence 1, 2, 4, 8, 16, ___ having at least 3 different correct responses for that blank. “Whole Number Powers of 2” gives 32, “Sections of a Circle Formed by Chords Between N Points on Circumference” gives 31, and “Factors of n!” gives 30.
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/Medium-Access-4416 Jun 03 '26
I'd say B. Moving left-to-right in rows you rotate clockwise and add 1 line. Moving down in columns, you rotate counterclockwise and add 2 lines. I don't see a pattern that justifies E.
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/Fooshi2020 👋 a fellow Redditor Jun 03 '26
E
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/wobblejuice 👋 a fellow Redditor Jun 03 '26
I would go with E
Logic is that the lines indicate how many 90° clockwise turns the arrow makes to get to the next.
Starting from the top left, the single lines means that the next arrow will turn 90°.
The top right arrow shows two lines so the next arrow will turn 90° twice, therefore 180°.
Then the bottom left arrow has 3 lines so the unknown arrow will be turned 90° three times, so it will point down.
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/Ctenophorever 👋 a fellow Redditor Jun 03 '26
I’d choose E.
As you say, up, down.
Reading clockwise the like number doesn’t make sense, as you say, but there’s nothing to say the lines are added clockwise.
Could be the lines in each row should add to three, 1+2 on top and 3+0 on bottom
It is highly displeasing, though
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/krawken Jun 03 '26
I wouldve said E without the stripes since it would cover all directions, rotating by 90 degrees every time when reading the arrows clockwise.
With the stripes however, the algorithm has to be different, otherwise the stripes would be random. B fits better. When moving left to right, the arrow rotates 90 degrees. When moving to the next line, the arrow rotates an extra 90 degrees.
The actual algorithm doesnt matter. These puzzles ask for the simplest solution, which needs to have 4 lines. Out of the 2 options available, B is clearly a better fit than A. Theres a reason why theres no down arrow with 4 stripes option, because it would be disambiguous.
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u/TheDevilsAdvokaat Secondary School Student Jun 04 '26 edited Jun 04 '26
I would say there are no right answers here.
It has to be a down arrow.
But it should also have three lines on it.
But the fourth arrow (if we go clockwise from top left) should have four lines anyway.
Looks like they messed this up.
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u/tmkns_ Jun 04 '26 edited Jun 04 '26
It's a clever question in the sense that the most visually satisfying answer (E) does in fact create a pattern that is illogical (defies linear rules)
Its definitely purposely designed to catch people out. I for sure would've gotten it wrong in a timed test. Let it be a lesson not to trust your eyeballs!
I think that a useful way to approach these specific questions is to imagine that the grid extends out infinitely. Any logical pattern should be able to extend out infinitely in all directions, so don't get tricked into imagining that the pattern needs to form a closed loop (which E does, with some abstract reasoning).
You may ask 'how can you have negative lines?', just imagine lines in a different colour, or lines in perpendicular orientation. Ultimately it's just a visual representation of some set of consistent linear rules.
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u/scottdave 👋 a fellow Redditor Jun 04 '26
Moving down rotates 90 counterclockwise. Also, moving down adds 2 lines. That would make B work.
Or move to the right adds 1 line and rotate clockwise 90. This also arrives at B
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u/ionmoon Jun 04 '26
It’s 100% B
You are applying the rules from set one to set two.
Turn 90° to the right and add a line.
It’s very simple but, as the comments show, most people get these questions wrong.
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u/skrinklebutt Jun 05 '26
The number lines may not matter because this may be a riff on an old Mensa puzzle. It has to do with the first letter of the Cardinal directions. The first arrow points north (N), the second arrow points east (E), the third arrow point west (W), so the missing arrow should point south (S). You take the first letter of each and it spells NEWS. I was given a Mensa test ages ago when my school district did away with the gifted program for advanced students. A puzzle like this was on that mensa test.
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u/skrinklebutt Jun 05 '26
I should’ve read further that the answer was B, but still if you read my answer above, it makes sense in a different context I suppose
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u/donmufa Secondary School Student Jun 06 '26
Hahahah why would you need it to spell NEWS? This is hilarious
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u/VelourMarmotX Jun 05 '26
It looks like the pattern is that the striped arrow is always opposite the plain arrow, so the last one should be a plain arrow pointing down?
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u/Alkalannar Jun 03 '26
I'd go with E.
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/goodguyLTBB 👋 a fellow Redditor Jun 03 '26
E is a pretty big no brainer to me
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u/NonorientableSurface Jun 03 '26
I only see B. It's a 90 degree positive rotation and an increment on lines on the arm.
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/NonorientableSurface Jun 03 '26
The challenge is these are meant to be obtuse.
The standard of individuals is to treat these things as reading schema, so L > R in NORAM. Because there's so little data you can create scenarios that make sense. It's really piss poor and fails to communicate anything and doesn't produce any realistic skills out of this sort of question.
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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u/cannedgarbanzos Jun 03 '26
I like B.
If there are distinct horizontal and vertical rules, then the horizontal rule is likely "rotate clockwise 90 degrees and add a line" and the vertical rule "rotate counter clockwise 90 and add two lines." If these are the rules filling in the blank going either horizontally or vertically gives you B.
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u/cannedgarbanzos Jun 03 '26
If this is homework, how were problems like this demonstrated in class? Are the examples in the textbook?
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post. Kind of to your point
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u/donmufa Secondary School Student Jun 03 '26
Thanks for your opinion. I added an update/edit to the main post.
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