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6 T-shirts

© Julia Nurit Schönnagel, MATH+

© Julia Nurit Schönnagel, MATH+

Author: Hajo Broersma (Universiteit Twente)
Project: 4TU.AMI

Challenge

33 pixies are standing in a circle. Each of the pixies is wearing either a red or a green T-shirt. If two pixies are direct neighbors in the circle, at most one of them is wearing a red T-shirt. If two pixies in the circle are separated by exactly 15 other pixies, at most one of the two is wearing a red T-shirt.

What is the largest possible number of pixies with a red T-shirt?

Possible answers:

  1.  The largest possible number of pixies with a red T-shirt is 7.
  2.  The largest possible number of pixies with a red T-shirt is 8.
  3.  The largest possible number of pixies with a red T-shirt is 9.
  4.  The largest possible number of pixies with a red T-shirt is 10.
  5.  The largest possible number of pixies with a red T-shirt is 11.
  6.  The largest possible number of pixies with a red T-shirt is 12.
  7.  The largest possible number of pixies with a red T-shirt is 13.
  8.  The largest possible number of pixies with a red T-shirt is 14.
  9.  The largest possible number of pixies with a red T-shirt is 15.
  10.  The largest possible number of pixies with a red T-shirt is 16.
Challenge as PDF