Teacher is so Smart

After studying roman numerals for a short time, the teacher had given the class some free time.  Sally's teacher walked up to her desk and saw that she had written:

XI + I = X

on her paper.

He was quick to point out her mistake.  Sally protested, saying she had it right.  After demonstrating what she meant, the teacher apologized and moved on.

What did Sally point out?

Helen and Who Are Not Very Close

Yesterday evening, Helen and her husband invited their neighbours (two couples) for a dinner at home. The six of them sat at a round table. Helen tells you the following:

1. Victor sat on the left of the woman who sat on the left of the man who sat on the left of Anna.
2. Esther sat on the left of the man who sat on the left of the woman who sat on the left of the man who sat on the left of the woman who sat on the left of my husband.
3. Jim sat on the left of the woman who sat on the left of Roger.
4. I did not sit beside my husband.

What is the name of Helen's husband?

Random Walk

A drunk leaves a bar (rather forcefully).  After standing up and dusting himself off (rather unsuccessfully), he decides to walk home.  Unfortunately for him, he has no idea where home is and has no way of deciding which way to go.  He is on a street traveling east-west only, making things simpler for him.

With each step, he's just as likely to turn around and walk back in the direction he came from.  After 20 steps, how likely is it he will be back where he started from (right in front of the bar)?

Time to Play

It goes up, but at the same time goes down. Up toward the sky, and down toward the ground. It's present tense and past tense too, come for a ride, just me and you.

What is it?

Split the Tab

You've been out to a restaurant with a group of people from work. The bill is now on it's way. Time for either a bit of philosophy/game theory. What's the best way to handle the bill? You have three choices: Split the bill evenly, pay for what you ordered, or got to the trouble of asking for separate checks?

For a good write up on the problem, try mindyourdecisions.

Not Exactly Chicken Nuggets

On a nice summer day, two tourists visit the Dutch city of Gouda. During their tour through the center they spot a cosy terrace. They decide to have a drink and, as an appetizer, a portion of hot bitterballs. The waiter tells them that the bitterballs can be served in portions of 6, 9, or 20.

What is the largest number of bitterballs that cannot be ordered in these portions?

Class is Almost Over

The gentlemen Dutch, English, Painter, and Writer are all teachers at the same secondary school. Each teacher teaches two different subjects. Furthermore:

• Three teachers teach Dutch language
• There is only one math teacher
• There are two teachers for chemistry
• Two teachers, Simon and mister English, teach history
• Peter doesn't teach Dutch language
• Steven is chemistry teacher
• Mister Dutch doesn't teach any course that is taught by Karl or mister Painter.

The Question: What is the full name of each teacher and which two subjects does each one teach?

In case anything has been missed:
The four first names are Karl, Peter, Simon, and Steven
The last four names are Dutch, English, Painter and Writer.
The classes are Chemistry, Dutch, History and Math.