An old auto is to drive a stretch of 2 miles, up and down a hill. Because the auto is so old, you cannot drive the first mile (the ascent) faster than 15 miles per hour.
How fast do you have to drive the second mile (going down the hill) in order to get an average speed of 30 miles per hour? Riddle Answer
Below are six discs stacked on a peg. The object is to reassemble the discs, one by one, in the same order on another peg, using the smallest number of moves. No larger disc can be placed on a smaller disc. How many moves will it take?
In a long, narrow chute there are 8 balls: 4 black ones on the left, and 4 white ones-slightly larger-on the right. In the middle of the chute there is a small niche that can hold 1 ball of either color. The chute’s right end has an opening large enough for a black but not a white ball.
Roll all the black balls out of the chute. You can’t pick them up from the chute. Riddle Answer
There are five squares formed by 12 matchsticks as shown in the figure. Can you remove just two matchsticks so that only two squares remain?
Three pennies and three nickles are arranged in a row. The pennies are red and nickles are green in color. The goal is to move them so that the coins are again in a row, with all pennies to the right and nickels to the left.
Each move consists of moving a pair of adjacent coins, and sliding those two coins to a new position without rotating the coins. How can you achieve this (shown below) in three moves?