Math Riddles

 
Popular
Daily Shuffle
New
Hard

60.9k views
38 ratings
1 saves

Question: Every time a man lies his nose grows to 150 percent of its size. Every time he tells the truth it shrinks to 50 percent of its size.

What will happen if he alternates between lies and the truth?

Answer: For every pair of a truth and a lie his nose will shrink to 75 percent of its previous size prior to this truth and lie. So the correct answer is 0. As the number of times he tells a lie and the truth ((3/4)n) approaches infinity the length of his nose approaches 0.

Share this:FacebookTwitterGoogle+

18.7k views
32 ratings
3 saves

Question: Ants on a stick may only move left or right. If they bump into each other they bounce off of each other and immediately move in the opposite direction maintaining speed the entire time. The only time they change speed is when they fall off of the edge of the stick.

If 25 ants are randomly put on a 1 meter long stick moving 1 meter per second, what is the longest amount of time it could take for them to all fall off?

Answer: The answer is 1 second.

Imagine that each ant is holding a flag and that when an ant bumps into another ant it gives its flag to the other ant. In this way, every ant always has a flag and a flag would never change direction. So each flag would head towards the edge at a rate of 1 meter per second and since the stick is 1 meter long, it would only take 1 second at most for each flag to fall off, and in turn, each ant.

Share this:FacebookTwitterGoogle+

94.5k views
119 ratings
4 saves

Question: An ant gets onto one end of a tight rope that is 1 meter long. The ant is traveling at 1 centimeter per second, but the entire rope is being stretched an extra 1 meter (1,000 centimeters) a second (it can be stretched forever).

Will the ant ever reach the other end of the rope?

Answer: He will reach the end of the rope eventually. Once he gets onto the rope, the rope behind him also stretches, so this must also be accounted for.

Share this:FacebookTwitterGoogle+
3 coins (medium)

13.9k views
18 ratings
0 saves

Question: You have three coins. One always comes up heads, one always comes up tails, and one is just a regular coin (has equal change of heads or tails). If you pick one of the coins randomly and flip it twice and get heads twice, what is the chance of flipping heads again?

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.

Share this:FacebookTwitterGoogle+

44k views
37 ratings
2 saves

By gandalf

Question: Everyday a peasant must pay the king one pound of gold and leave it on a collection plate in front of his house. Every morning a guard comes by to make sure he has put a pound of gold on the plate. The king collects the gold every six days from the plate. If the peasant only has one six pound block of gold, how can he make only two parallel cuts and still follow the kings rules each day?

Answer: He can cut one pound off and two pounds off. This would leave a one pound, two pound, and three pound block. On the first day he leaves the one pound block. On the second day he leaves the two pound block. On the third day he leaves the three pound block. On the fourth day he leaves the three pound and one pound blocks. On the fifth day he leaves the three pound and two pound blocks. On the last day he leaves all of them.

Share this:FacebookTwitterGoogle+

Submit Your Riddle

Follow Us

Follow us and get the Riddle of the Day, Joke of the Day, and interesting updates.

Advertise with us!

© 2013-2014 Good Riddles Now. All rights reserved.

FacebookTwitterGoogle+RSS Feed