## Monday, May 12, 2008

### A Substitute Teacher

A substitute teacher has been tipped off about a girl cheating in his class. Unfortunately, he doesn't know the class well enough to know who's friends with who. Fortunately, there are only four girls in his class. One of the girls is lying about cheating. A second girl is her friend and wants to help her friend (especially since she's worried that she might be implicated!). The other two girls are innocent and will tell the truth.

Andrea: "Dottie is the cheater."
Beatrice: "Charlene is lying."
Charlene: "Andrea is lying."
Dottie: "Beatrice is not the friend."

1. logic - use process of elimination. look for the two people telling the truth. Assume the other two are lying

(girls called A, B, C, D)

can't be (truthful):
AC
AB (because dottie would also be telling the truth)
BC
BD (because then charlene would have to be telling the truth)

therefore it has to be Charlene and Dottie telling the truth

therefore, beatrice is cheating, andrea is her friend.

i could be wrong, but that's what i came up with

can be (truthful)

2. Better solution.
The teacher makes four different tests, and makes sure that each girl gets a different test.
Problem solved.

3. I like your second solution. A bit unfair to the girls who are being truthful, though.

Leave your answer or, if you want to post a question of your own, send me an e-mail. Look in the about section to find my e-mail address. If it's new, I'll post it soon.

Please don't leave spam or 'Awesome blog, come visit mine' messages. I'll delete them soon after.

Enter your Email and join hundreds of others who get their Question of the Day sent right to their mailbox