# Calvin Goes to Ten Flags

**Discrete Mathematics**Level 3

Over the summer, Calvin, along with a group for friends, went to Ten Flags (an amusement park). There are 10 "must-ride" roller coasters. At the end of the day, everyone rode exactly 5 of these 10 rides (due to the dastardly long lines). Furthermore, any 2 different people rode at most 2 rides in common. What is the highest possible number of people in this group?

**Details and assumptions**

Calvin is to be included in the count. You should not exclude him from amusement parks.

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