Saturday, August 19, 2017

Factor Sums


Not counting itself, the number 6 has the factors 1, 2, and 3, which add to 6. The number 28 has the same property (its factors are 1, 2, 4, 7, and 14). Can you come up with a three-digit number that has this property? What about a four-digit number? Click below for the answers.


Saturday, August 12, 2017

Minimum Percentage


75% of men from a certain group are tall, 75% have brown hair, and 75% have brown eyes. What is the minimum percentage that are tall, have brown hair, and have brown eyes? Click below to see the answer.


Saturday, August 5, 2017

A Two-Digit Number


Find a two-digit number that's equal to two times the result of multiplying its digits. Click below to see the answer.




Saturday, July 29, 2017

Identical Twins


Alice and Eve are identical twin sisters. One always lies and the other always tells the truth, but we don't know which is which. We ask one of them "Is Alice the one that always lies?" and she replies "Yes." Did we speak to Alice or Eve? Click below to see the answer.



Saturday, July 22, 2017

Counting Socks


All my socks are red except two. All my socks are white except two. All my socks are blue except two. How many socks do I have? Click below for the answer.


Saturday, July 15, 2017

Circumnavigation


From 1519 until 1522, Ferdinand Magellan's Victoria was the first ship to successfully circumnavigate the globe. (Magellan himself did not survive the entire voyage.) Can you tell me which part of the ship traveled the greatest distance? Click below for the answer.




Replica of the Victoria, Photograph by Gnsin - Own work, CC BY-SA 3.0

Saturday, July 8, 2017

50 factorial


50! = 30414093201713378043612608166064768844377641568960512071337804000

Without doing the full computation, can you tell whether the above statement is true or false? Click below for the answer.