When the Combination Calculator seems to misbehave, the cause is usually one of two things: something stopped the tool from running, or it ran but the result is not usable. This guide starts with the fastest checks, then walks through the common problems and exact fixes.
Quick Checks First
- Refresh the page - a stalled session is the most common cause of nothing happening.
- Confirm the input is not empty and actually contains what you meant to submit.
- Try the smallest possible input; if that works, the issue is size, not the tool.
- Turn off browser extensions that block scripts, then reload and test again.
- Update or switch browsers if the problem repeats across sessions.
Common Problems and How to Fix Them
My answer is smaller than the answer key.
If order matters in your problem you needed permutations - rerun it with the permutation calculator.
The numbers do not cancel the way I expected.
Divide by r! as well as (n - r)! - both factorial parts must go for an unordered count.
I entered the values the wrong way round.
n is always the pool size and r the amount taken, so swap them and recalculate.
The result seems too large.
Combinatorics grows fast - 30C3 is already 4,060, so big counts are normal.
My manual count differs by a few.
Manual enumeration usually misses or repeats a group - trust the formula and re-list carefully if you doubt it.
Choosing nothing or everything gave odd results.
Both cases are sensible: nC0 is 1 and nCn is 1, a single way each.
When It Works but the Output Is Poor
If the tool runs fine but the result misses, the problem is almost always the brief, not the software:
- Counting ordered outcomes with nCr
- Entering r larger than n
- Mixing up the r and n positions
- Double counting groups in manual checks
How to Stop It Happening Next Time
- Keep a saved prompt template for every task you repeat.
- Change one setting per generation so causes stay obvious.
- Run a two-minute sanity test with known input after any update.
- Note every failure and its fix; a short troubleshooting log pays for itself.
Still Stuck?
Reproduce the problem with the smallest possible input and note the exact steps that triggered it. A one-line description of what you did, what you expected and what happened is enough to get a precise answer from support or a colleague.
Frequently Asked Questions
What does nCr count?
It counts distinct groups of r items drawn from a pool of n where the order inside the group is ignored.
When do I use combinations instead of permutations?
Use combinations whenever rearranging the same items still gives the same outcome, such as a committee or a hand of cards.
What is the formula?
nCr equals n factorial divided by r factorial and (n - r) factorial multiplied together.
Is my input stored?
No - the calculation runs in your browser.
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