### Bat Wings

Two students collected some data on the wingspan of bats, but each lost a measurement. Can you find the missing information?

### Kate's Date

When Kate ate a giant date, the average weight of the dates decreased. What was the weight of the date that Kate ate?

### Balancing the Books

How many visitors does a tourist attraction need next week in order to break even?

# Number of Arms

##### Age 11 to 14 ShortChallenge 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.