In a village, friendship among girls is mutual. Each girl has either exactly one
friend or exactly two friends among themselves. One morning, all girls with two
friends wear red hats and the other girls all wear blue hats. It turns out that any
two friends wear hats of different colours. In the afternoon, 10 girls change their
red hats into blue hats and 12 girls change their blue hats into red hats. Now it
turns out that any two friends wear hats of the same colour. How many girls are
there in the village? (A girl can only change her hat once.)

• Total girls are 48.
  
  Earlier 16 girls with red hat and 32 girls with blue hat.
  All the girls are grouped in 16 groups .
  In each group one girl wearing red hat is friend of other two girls wearing blue hats.
  
  In afternoon, In 10 groups girl wearing red hat changed her hat to blue hat.
  and in other 6 groups ,12 girls wearing blue hats changed to red hats.
  
• 12 years agoHelpfull: Yes(3) No(0)
• 22
  red=10
  blue=12
  because all girl changing hats and only once so 10+12 should be the answer
• 12 years agoHelpfull: Yes(0) No(2)