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Problem
Getting Started
Student Solutions
Teachers' Resources
Proximity
Age 14 to 16
Challenge Level
We are given a regular icosahedron having three red vertices. Show that it has a vertex that has at least two red neighbours.
If you're stuck, try this
proof sorting activity
.
This problem was taken from the Hungarian magazine KoMaL. There are many other challenging problems in English on
the KoMal website
.