This week's new problems have just gone up, but the 300-point Combinatorics problem says "Solved by 54 users" already, including Harshit S. solving it 210 days ago. What's going on?

We do recycle problems used in past problem sets for a variety of reasons. We do our best to assign you a problem that you haven't seen, or had answered wrongly previously.

Currently, I'm doing an analysis into the consistency of problem difficulties over time, and to understand how the cohort of members have changed over the past year.

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TopNewestWe do recycle problems used in past problem sets for a variety of reasons. We do our best to assign you a problem that you haven't seen, or had answered wrongly previously.

Currently, I'm doing an analysis into the consistency of problem difficulties over time, and to understand how the cohort of members have changed over the past year.

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OK. Thanks for the explanation :)

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Also "No 3's allowed" has been solved by 430 people, but the other two problems (visible at level 5) have only been solved by 1 person.

Maybe the "Solved by N users" bubble is finding past problems that had the same title, or something?

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Sometimes, problems are recycled from long ago.

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Check out this post: https://brilliant.org/discussions/thread/repeted-problems/

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