Showing posts with label puzzles. Show all posts
Showing posts with label puzzles. Show all posts

Sunday, June 17, 2007

A riddle.

A man is being hanged. There is a man in the crowd of observers who is asked of his relation to the guy on the gallows. He doesn't want to admit it, so he answers in a riddle:

-Brothers and sisters I have none, but that man's father {pointing to the man about to be hanged} is my father's son.

What is the relation between the condemned and the man in the crowd?

Sunday, January 14, 2007

Object of interest

Some time ago my friend asked me an interesting question: what body (possessing internal volume) has three orthogonal projections being circles (of the same radii), but isn't a sphere. I could imagine a stationary view of such object, but couldn't really rotate it in my head. I guess, my rendering software needs some practice ;-). Sasha Parfenov (my friend) actually made it out of paper. At first I thought about making it out of Styrofoam using a cookie-cutter technique, but instead I decided to read AutoCAD manual a bit more. After ~1 hour of reading and tweaking the object was drawn and rendered from different angles:Orthogonal projections:It would be really cool to machine this body on lathe (from brass). Maybe in a very distant future it will happen. But for now here is the next best thing:I couldn't find description of this body in any of my math books nor on the Internet. A hypothesis that it is a "cylindroid" wasn't correct. One definition of cylindroid is:
cyl·in·droid
n.
1. A cylindrical surface or solid all of whose sections perpendicular to the elements are elliptical.
2. A mucous thread with pointed or split ends, observed microscopically in the urine, and resembling a urinary cast.
adj.
Resembling a cylinder.
Cylindroid is also a different name for Plücker's conoid. It would be interesting to find out the actual name of this body.

P.S. The object's name is a tricylinder. The general name for a body formed by an intersection of cylinders is Steinmetz Solid. Looking through some of the 3D objects on WolframMathWorld, I finally found it after searching for "intersecting cylinders". The 3D applet they use is very cool and many shapes are pretty interesting

Saturday, January 13, 2007

Stale cucumbers' problem

A vegetable-storage facility got 100 tonnes of cucumbers. The humidity analysis showed they contained 99% of water. After storing them for a month they were analyzed again, showing that water content dropped to 98%. What is the total weight of cucumbers after a month storage?
Courtesy OGP