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: If you're 8 feet away from a door and with each move you advance half the distance to the door. How many moves will it take to reach the door?
Answer: Infinity! Technically you will never reach the door, as you can only move half the distance, no matter how small.
Riddle: You want to boil a two-minute egg. If you only have a three-minute timer (hourglass), a four-minute timer, and a five-minute timer, how can you boil the egg for only two minutes?
Answer: Once the water is boiling, turn the three-minute timer and five-minute timer over. When the three-minute timer runs out, put the egg in the boiling water. When the five-minute timer runs out, two minutes have elapsed and it is time to take the egg out of the water. You don't need the four-minute timer for this riddle.
Riddle: If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?
Riddle: When John was six years old he hammered a nail into his favorite tree to mark his height. Ten years later at age sixteen, John returned to see how much higher the nail was. If the tree grew by five centimeters each year, how much higher would the nail be?
Answer: The nail would be at the same height since trees grow at their tops.
Riddle: A farmer in California owns a beautiful pear tree. He supplies the fruit to a nearby grocery store. The store owner has called the farmer to see how much fruit is available for him to purchase. The farmer knows that the main trunk has 24 branches. Each branch has exactly 12 boughs and each bough has exactly 6 twigs. Since each twig bears one piece of fruit, how many plums will the farmer be able to deliver?
Answer: None. A pear tree does not bear plums.