A riddle problem is a question or statement intentionally phrased so as to require ingenuity in ascertaining its answer or meaning, typically presented as a game.  Below is a list of the past problem of the week riddles in descending chronological order.

Riddle: A sphere has three, a circle has two, and a point has zero. What is it?
Riddle: The rungs of a 10-foot ladder attached to a ship are 1 foot apart. If the water is rising at the rate of one foot an hour, how long will it take until the water covers the ladder?
Answer: It will never cover the ladder because as the water rises, so will the floating ship.
Riddle: One is to three as three is to five and five is to four and four is the magic number.  What is the pattern?
Answer: One has three letters in the word three has five letters in it five has four letters and four has four letters in it (if you try more numbers they will always come back to the number four: so four is the magic number)
Riddle: How do you make the number 7 even without addition, subtraction, multiplication, or division?
Answer: Drop the "S" and "seven" becomes "even".
Riddle: How can you write down eight eights so that they add up to one thousand?
Answer: 888 + 88 + 8 + 8 + 8 = 1000.
Riddle: How can you measure nine minutes with have two hourglasses, one four minute and one seven minute?
Answer: Turn over both hourglasses at once. When the four-minute hourglass runs out, turn it over. When the seven-minute hourglass runs out, turn it over. When the four-minute timer runs out this time (eight minutes have elapsed), the seven-minute hourglass has been running for one minute. Now turn over the seven minute timer back over. When the timer runs out, nine minutes have elapsed.