No one of us knew the age of Lisa, our math teacher, and the six guesses were as follows:
34,47,48,53,30 and 40.
When confronted with this list , Lisa joyfully said:
I will not disclose my age explicitly, but I let you know that all of you erred.
Your estimates were off by: 2,6,11,12,8,5.

Well, it took some reasoning to get her true age.

What was it?

The range of the students' guesses is 53 - 30, or 23. Since neither "student 30" nor "student 53" was off by more than 11 or 12, Lisa's age must fall within this range -- specifically, she's either 41 or 42. The closest guess was off by 2; this must be "student 40." So Lisa is 42 years old!

Posted by Jyqm on 2010-10-14 13:19:49