11 Good Math Riddles

By: Justin Zablocki (author, Zablocki Bros. LLC) on September 4th, 2013 12:00 AM.

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Math and riddles go perfectly together because they are both children of logic. Math riddles combine mathematical theory and techniques with classic word riddles to make a fun and tricky new riddle. These riddles are organized easiest to hardest. How many and how fast can you solve them?

1. There are 11 bananas and you take 4, how many do you have?
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2. You have 2 coins that add up to 35 cents. One of the coins is not a quarter.
   
   What kind of coins do you have?
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3. How can you add 8 8's to make 1000?
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4. What number do you get when you multiply all of the numbers on a telephone's number pad?
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5. On a clock, how many times a day do the minute and hour hand overlap?
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6. If you have an 11 minute and 13 minute hourglass, how can you accurately time 15 minutes?
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7. There are 100 coins scattered in a dark room. 90 have heads facing up and 10 are facing tails up. You cannot tell which coins are which. How do you sort the coins into two piles that contain the same number of tails up coins?
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8. There is a chain nailed to the wall. The chain is 10 feet long and the center of the chain dips down 5 feet from where each side of the chain is nailed to the wall. How far are the 2 ends of chain from each other?
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9. You have a glass of water that looks about half full. How can you tell, only using the glass of water itself, if the glass is half full or not?
   
   The glass is a right cylinder.
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10. Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a sports car; behind all of the others is bicycles. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 2, revealing a bicycle. He then says to you, "Do you want to pick door No. 3?" Is it to your advantage to switch your choice?
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11. Three guests check into a hotel room. The clerk says the bill is $30, so each guest pays $10. Later the clerk realizes the bill should only be $25. To rectify this, he gives the bellhop $5 to return to the guests. On the way to the room, the bellhop realizes that he cannot divide the money equally. As the guests didn't know the total of the revised bill, the bellhop decides to just give each guest $1 and keep $2 for himself. Each guest got $1 back: so now each guest only paid $9; bringing the total paid to $27. The bellhop has $2. And $27 + $2 = $29 so, if the guests originally handed over $30, what happened to the remaining $1?
    Answer
    
    

I hope you enjoyed these good math riddles, for more math riddles visit Good Riddles Now's math section