What Does "Which of the Following Is Not Possible" Actually Mean
You've seen it on tests. Plus, that frustrating little phrase — "which of the following is not possible" — shows up everywhere from standardized exams to late-night puzzle books. You've seen it in brain teasers. And honestly, it can feel like a trick question no matter how prepared you are.
But here's the thing — these questions aren't actually about memorizing answers. They're about understanding how logical reasoning works. Once you get that, solving them becomes way easier Practical, not theoretical..
So let's talk about what these questions really are, why they show up so often, and how to tackle them without second-guessing yourself into oblivion.
What "Which of the Following Is Not Possible" Questions Actually Are
At its core, a "which of the following is not possible" question is a logical reasoning problem. You're given a set of conditions or scenarios, and you need to figure out which option breaks the rules somehow And that's really what it comes down to..
These questions test your ability to:
- Track multiple constraints at once
- Spot contradictions
- Understand what must be true versus what could be true
- Recognize when something violates a given rule
The key word here is not possible — not "not likely," not "not probable," but genuinely impossible under the stated conditions Nothing fancy..
Here's a simple example to show what I mean:
Three friends — Anna, Ben, and Carla — each have a different favorite color: red, blue, or green. Anna does not like green. Ben does not like blue. Which of the following is NOT possible?
- Anna likes red
- Ben likes green
- Carla likes blue
- Anna likes blue
If you work through it: Anna can't be green, Ben can't be blue. Here's the thing — then Anna isn't green (good) and Ben isn't blue (good). But if Anna is blue? Also, that means Ben must be red or green. Worth adding: if Ben is green, then Anna must be red (since she can't be green), and Carla gets blue. That works. Even so, wait — actually, that works too. See how you have to test each option against the constraints?
That's the basic idea. You're not looking for the right answer — you're looking for the answer that cannot work Simple as that..
Why These Questions Show Up So Often
Here's the thing: these questions show up on the LSAT, the GMAT, IQ tests, and countless aptitude tests for a reason. They measure something real — your ability to process information systematically and spot logical inconsistencies.
In the real world, this matters more than you'd think. Worth adding: lawyers build cases by finding what cannot be true given the evidence. Engineers identify failure modes by understanding what cannot happen under certain conditions. Even everyday arguments often come down to "well, that can't be right because.. Most people skip this — try not to..
This changes depending on context. Keep that in mind.
So these questions aren't just academic busywork. They're testing a skill that actually matters.
How to Approach These Questions
Here's the part where I give you the actual strategy, because honestly, most people approach these wrong.
Step 1: Identify All the Constraints
Before you look at the answer choices, write down every condition you're given. Also, every single one. Don't assume anything isn't important That's the part that actually makes a difference..
Step 2: Test Each Answer Against Those Constraints
This is where people waste time. Think about it: they try to figure out which answer could work, then hope they didn't miss something. Wrong approach Easy to understand, harder to ignore..
Instead, take each answer choice and ask: "If this were true, would it violate any of the stated conditions?"
If yes — that's your answer. That's the one that's not possible Less friction, more output..
Step 3: Watch for Hidden Assumptions
One reason these questions trip people up is that we naturally make assumptions that aren't in the problem. The test isn't checking whether you're smart — it's checking whether you only use the information provided.
Here's one way to look at it: if the question says "four people each own a different pet," you might assume they can't share a pet. But what if the question allows one person to own multiple pets? You'd need to actually read the conditions Took long enough..
Step 4: Look for Contradictions
Most "not possible" answers involve a direct contradiction — two things that can't both be true at the same time. Train yourself to spot when an answer creates a logical conflict with the given rules.
Common Mistakes That Trip People Up
Let me be honest — I've watched smart people miss these questions for the same reasons over and over. Here's what goes wrong:
Assuming more rules than exist. Sometimes the conditions are deliberately minimal. People add extra constraints that aren't there, then eliminate answers that would actually work.
Testing only the "obvious" answers. We tend to check the first couple options carefully and then rush through the rest. But sometimes the right answer is hiding in the last option It's one of those things that adds up. Which is the point..
Confusing "not possible" with "not likely." Just because something feels unlikely doesn't mean it's impossible. These questions are about logical impossibility, not probability.
Not re-reading the question. Seriously — how many times have you answered "which is possible" when it said "which is NOT possible"? It happens more than you'd think.
Practical Strategies That Actually Work
Here's what I'd do if I were taking a test with these questions:
Use the process of elimination. If you can prove an answer could be true, cross it off. Keep going until only one answer remains that definitely violates the rules.
Draw it out. For questions involving ordering, scheduling, or assignments, a simple diagram helps enormously. A timeline, a grid, even just writing names in a list — anything that makes the constraints visual.
Start with the most constrained element. If one person or item has the most rules attached to it, figure out their situation first. That often narrows everything else down Surprisingly effective..
Check your work backwards. Once you think you've found the answer, re-read the conditions and verify that your answer actually violates at least one of them. If you can't find the violation, you might have the wrong one That alone is useful..
Frequently Asked Questions
Can "which of the following is not possible" questions ever have more than one impossible answer?
In a well-designed question, no. There should only be one answer that definitively violates the given conditions. If you find multiple that seem impossible, you've likely misread the constraints or added rules that weren't stated.
What's the difference between "not possible" and "not necessarily true"?
"Not possible" means it absolutely cannot happen under any interpretation of the rules. Practically speaking, "Not necessarily true" means it might be false — it's not guaranteed. These are different logical standards, and confusing them is one of the most common errors.
Do I need to memorize common question patterns?
Not exactly — but understanding that these questions follow predictable structures helps. Most involve either direct contradictions, transitive logic (if A > B and B > C, then A > C), or constraints about what can and cannot coexist.
What if I can't figure out which answer is impossible?
Try assuming each answer is true, one at a time, and see if you can make it work with all the given conditions. If you hit a wall with one answer — you can't make it fit no matter how you arrange things — that's probably your answer.
The Bottom Line
"Which of the following is not possible" questions aren't about being clever or having some special talent. They're about being systematic. Consider this: read the rules. That said, test each option. Look for the contradiction.
That's it.
The reason these questions feel tricky is that we're trained to look for the "right" answer. But here, you're looking for the answer that breaks the rules. Once you shift your mindset to that, everything gets simpler And it works..
So next time you see one of these, don't panic. Just work through it step by step. You'll get there That's the part that actually makes a difference..
