6. In the village of Monkeyville, every boy knows all the girls who know him, and among the acquaintances of each girl, the number of boys is greater than the number of girls. Prove that in Monkeyville, there are no fewer boys than girls.
## 7th grade
This one wants a proof. Work it on paper, read the official solution, then mark
yourself honestly — the ladder only means something if the record is true.
Official solution
90.6. See the solution of problem 90.19, considering boys as knights and girls as liars.
Source: NuminaMath-1.5,
licensed Apache-2.0.
Statement and solution reproduced as published; topic, difficulty and ordering added
by this site.