Department of Mathematics - NC State University

Driving along, Terry notices that the last four digits on the odometer are palindromic. A mile later, the last five digits are palindromic. Two miles later, all six are palindromic. What was the odometer reading when Terry first looked at it?

Answer:
1-9-8, 8-8-8. That's what he first saw when he looked.
One mile later it was 1-9-8, 8-8-9, the last five are palindromic.
One mile later, 1-9-8, 8-9-0, the middle four are palindromic. You
drive one more mile and it's 1-9-8-, 8-9-1, all six are palindromic.

Riddle #1 from Fall 2007 Newsletter

A boat has a ladder that has six rungs, each rung is one foot apart. The bottom rung is one foot from the water. The tide rises at 12 inches every 15 minutes. High tide peaks in one hour. When the tide is at it's highest, how many rungs are under water?

Answer: No rungs will be under water; the boat floats.

Riddle # 2 from Fall 2007 Newsletter

There are 4 men who want to cross a bridge. They all begin on the same side. You have 17 minutes to get all of them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them. The flashlight must be walked back and forth, it cannot be thrown, etc. Each man walks at a different speed. A pair must walk together at the rate of the slower man.
Man 1: 1 minute to cross
Man 2: 2 minutes to cross
Man 3: 5 minutes to cross
Man 4: 10 minutes to cross

Answer:
Man 1 and Man 2 cross 2 min
Man 2 comes back 2min
Man 3 and Man 4 cross 10 min
Man 1 comes back 1 min
Man 1 and Man 2 cross 2 min
Total 17 min