# Math Riddles

##### Math Riddle #131 (hard)

Question: If you have an 11 minute and 13 minute hourglass, how can you accurately time 15 minutes?

##### Math Riddle #259 (medium)

Question: If you have a rope around a soccer ball and the moon, which rope would have to increase in length more to create a one meter gap between the rope and the soccer ball/moon?

##### Math Riddle #303 (medium)

Question: A man taking the census walks up to the apartment of a mathematician and asks him if he has any children and how old they are. The mathematician says "I have three daughters and the product of their ages is 72." The man tells the mathematician that he needs more information, so the mathematician tells him "The sum of their ages is equal to our apartment number." The man still needs more information so the mathematician tells him "My oldest daughter has her own bed and the other two share bunk beds."

How old are his daughters?

##### Add a line to make it true (medium)

Question: How can you make the following true by adding a single line: .9 = 1.

Note: ≠ is not the answer.

##### Circular table of death (hard)

Question: There are 1600 people sitting around a circular table. The first person (person 1) has a sword and kills the second person then hands it to the next alive person (in this case person 3). Person 3 stabs person 4 and gives the sword to person 5. This goes on until person 1499 kills person 1500. Then person 1 kills person 3 and so on. This is repeated until there is only a single person remaining.

Who remains in the end?