Difference between revisions of "2020 AMC 12B Problems/Problem 15"
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15. There are 10 people standing equally spaced around a circle. Each person knows exactly 3 of the other 9 people: the 2 people standing next to her or him,as well as the person directly across the circle. How many ways are there for the 10 people to split up into 5 pairs so that the members of each pair know each other? | 15. There are 10 people standing equally spaced around a circle. Each person knows exactly 3 of the other 9 people: the 2 people standing next to her or him,as well as the person directly across the circle. How many ways are there for the 10 people to split up into 5 pairs so that the members of each pair know each other? | ||
| − | <math>(A) 11 (B) 12 (C) 13 (D) 14 (E) 15</math> | + | <math>(A) 11 (B) 12 (C) 13 (D) 14 (E) 15</math> |
Revision as of 21:16, 7 February 2020
15. There are 10 people standing equally spaced around a circle. Each person knows exactly 3 of the other 9 people: the 2 people standing next to her or him,as well as the person directly across the circle. How many ways are there for the 10 people to split up into 5 pairs so that the members of each pair know each other?
