Problem:
Students guess that Norb's age is , and . Norb says, "At least half of you guessed too low, two of you are off by one and my age is a prime number." How old is Norb?
Answer Choices:
A.
B.
C.
D.
E.
Solution:
Because half are too low, Norb is at least . Because two are off by one, he must be between and or between and . Because is prime and is not, Norb is .
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions