Monday, November 19, 2007

Mathematicians

Two mathematicians (let's call them M and N) – once good friends – meet after a long time to have a drink together. M asks, "Are you married? Any kids? Do you still live in that old apartment building?" N replies, "Yes, I'm married with three kids, and we live in a private house now." M asks, "How old are your kids?" N replies, "Let me answer with a riddle: The product of the ages of my kids is 36. Now, see that bus over there? The sum of my kids' ages is equal to that bus number." M thinks for a moment, then says, "I don't have sufficient information to solve the puzzle." N replies, "Oh, yes, you're right. I forgot to mention that one of my kids was born before we bought the house." Soon after N provides this last bit of information, M solves the puzzle and tells N the correct ages of the kids.

Can you figure out the solution? Also, how would the solution change if N's additional piece of information was that one of his kids was born after he bought the house?


Wednesday, September 05, 2007

Prisoners and Switches

A prison warden meets with 23 new prisoners when they arrive. He tells them, "You may meet today and plan your strategy for the challenge I'm about to propose. But after today, you'll be in isolated cells and will have no communication with one another. In the prison is a switch room, which contains two switches labeled A and B, each of which can be in either the On or Off position. The switches aren't connected to anything. I'm not telling you the switches' present positions. After today, from time to time, whenever I feel so inclined, I'll select one prisoner at random and escort him to the switch room. This prisoner will select one of the two switches and reverse its position. He must move only one of the switches. He can't move both switches, and he can't move neither switch. Then, I'll lead the prisoner back to his cell. No one else will enter the switch room until I lead the next prisoner there, and I'll instruct him to do the same thing. I'm going to choose prisoners at random. I might choose the same prisoner three times in a row, or I might jump around and come back. However, given enough time, everyone will eventually visit the switch room as many times as everyone else. At any time, if you're 100 percent certain, any one of you can declare to me, 'We have now all visited the switch room.' If that person is correct, I'll set you all free. If that person is wrong, and somebody hasn't yet visited the switch room, I'll feed you all to the alligators."

What strategy can the prisoners use to obtain freedom?


Saturday, August 18, 2007

Cryptogram

Solve the following cryptogram quote made by a famous person.


Ipial cfm O ciiz oj om jyci tfl cl jwdiaoya. -Afbdk Tfbhy Iciajym

Wednesday, August 08, 2007

Catching a Train

Two trains race toward each other on a railway segment that's 100 miles long. The trains are traveling at 100mph. An insect flying at 200mph flits from one train toward the other, and as soon as it arrives at the other, it flips its direction and flies back toward the first train. The insect continues bouncing back and forth between the trains until the trains crash. What's the total distance that the insect covers until the moment of the crash?


Monday, July 30, 2007

Toy Store

Our local toy store prices toys according to its own logic. A doll costs $17, a scooter costs $26 and a kite costs $14. Under the same system, how much will a top cost?


Family Ages

Kay is now 40 years old. Her son Phil is 13. How many years ago was Kay four times as old as Phil?


Monday, May 21, 2007

Different Trees

Sally and three of her friends decided to plant a new tree in their yard to celebrate Arbor Day. The new trees would each be put in a different area of their yards. As it happened each friend bought a different kind of tree and planted the new tree on a different day of the week. From the clues below, determine the full names of each friend, what kind of tree each bought, where in the yard it was planted, and on what day of the week each tree was planted.

  1. Wanda, whose last name wasn’t Frost, didn’t plant her spruce tree by the patio.
  2. Tracy planted her tree before Mrs. Dart but after the woman who planted the ash tree.
  3. Mrs. Best, whose first name wasn’t Sally, planted her tree in the front yard, but not on Friday.
  4. Rhonda didn’t plant her tree on Monday.
  5. Mrs. Grand planted her tree before the woman who planted her tree in the back yard. Rhonda didn’t plant the cherry tree.
  6. The trees were planted, in chronological order, as follows: Mrs. Frost, in the garden, Wanda, the maple tree.

The Farmer


Once there was a farmer who was taking apples to town for sale at a local market. On the way to town, he had to pay four tolls. Each toll cost one-half his apples plus half an apple. After paying all four tolls, the farmer arrived in town with no apples left to sell. Question : How many apples did the farmer start with?

Thursday, March 29, 2007

Coiled Words

An interesting statement is coiled in the grid below. To spell it out, start with one letter and move to an adjacent letter in any direction.

E

D

O

N

A

R

S

C

R

S

T

L

I

F

N

A

U

G

I

E

L

I

G

U

F

I

B

U

T

X

R

E


Bicycling

Nick decided to test out his new bicycle for the upcoming endurance race. He rode his bike at six miles per hour and arrived in the next town one hour earlier than if he had ridden at five miles per hour. How far did he ride?