Good Riddles

Answer: Your hands.

Answer: You should pick heads, tails, and tails. Both of them begin with heads then tails, giving you an equal chance of getting the first two. But if you have tails for the final flip and don't get it you are still 1/3 of the way through the sequence. If you have heads for the final flip and miss it you must start all over trying to get the sequence.

Answer: 7.5 degrees.

The minute hand is pointing directly at the '3'. The hour hand is 1/4 of the way between the '3' and '4'. Since there are 12 numbers the angle between each number is 30 degrees. So the angle between the hands are 30 degrees * 1/4 = 7.5 degrees.

Answer: A lock.

Answer: 90 percent. If you pick the heads coin the chance of getting the first 2 heads is 100 percent (4/4) and if you pick the fair coin the chance is 25 percent (1/4). So from this, the chance that it is the heads coin is 4/5 and the fair coin 1/5.

Then, if it is the heads coin you will definitely get heads (4/5). If you flip the fair coin it is 1/10 (1/5 * 1/2). Add the probabilities together: 4/5 + 1/10 = 9/10.