Handshakes and pairs

If everyone in a group of n shakes hands with everyone else, each person shakes n minus one hands, but every handshake involves two people, so the total is half of n times n minus one. The same shape counts games in a round robin and lines between points.

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LearnWhat it is, how to spot it, a worked example, and where it goes wrong.
Practice — 3-point ladder1 problem. Three in a row finishes it.0/3 in a row · 0/1 solved
Practice — 4-point ladder4 problems. Three in a row finishes it.0/3 in a row · 0/4 solved
Practice — 5-point ladderNo problems written at this tier yet.Nothing written at this tier yet
Skill quizFinish every ladder that has problems first.Finish the ladders above first

Before and after

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CNT-06Selections of a few objects

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Nothing yet. No other skill in the Atlas lists this one as a prerequisite.

In official papers

No indexed official paper question has been tagged with CNT-08 yet. The index grows one paper at a time, and it records only question numbers, point values and our own skill tags — never the problems themselves.

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