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Number of Arms

Age 11 to 14 Short Challenge Level:

We begin by assuming that almost everybody has 2 arms. Nobody has 3, but a small number of people have lost one or both arms in accidents or amputations. Here, we will ignore fractional arms - but you don't actually have to.

Measure What it is Value More than this many arms
Mean If all of the arms in the world were shared equally between all of the people Just below 2 2
Median The middle number, when everybody's number of arms is written in a long, ordered list:
0, ..., 0, 1, ..., 1, 2, ..........................................................., 2
2 3
ModeĀ  The most common number of arms 2 3

The next person you meet will probably have 2 arms, and definitely won't have more.

So it is almost certain that they have more than the mean number of arms, but impossibleĀ that they have more than the median or modal number of arms.




You can find more short problems, arranged by curriculum topic, in our short problems collection.