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Round manhole covers cant' fall into the manhole, while a square one could be placed diagonal...

Right answer. But, do you know why is it so? What property of a circle makes this true? Is it because the circle has constant diameter?

Is the circle the only shape with constant diameter?

Love is blind, but marriage is a real eye opener.

Never got any reply to my question that - what property of a circle makes it possible for a manhole cover to not fall down in the manhole?

Also, is a circle the only shape which has that property? Or, there exists a shape other then a circle, which will make the manhole cover to not fall inside the manhole?

Love is blind, but marriage is a real eye opener.

Okay, I give up. I was hoping to see some interesting replies to this one..anyways, I will go ahead and reveal the answer.

The circle isn't the only shape that would work safely as a manhole cover. Another possibility is the Reuleaux triangle, named after engineer Franz Reuleaux, who was a teacher in Berlin, more than a hundred years ago.

An example of a Reuleaux triangle can be found in your medicine cabinet. If you turn a bottle of NyQuil or Pepto-Bismol upside down, the shape you see looks like a Reuleaux triangle.

One way to draw a Reuleaux triangle is to start with an equilateral triangle, which has three sides of equal length. Place the pointed end of a pair of compasses at one corner of the triangle and stretch the arms until the pencil reaches another corner. Then draw an arc between two corners of the triangle. Draw two more arcs centered on the triangle's other corners.

This "curved triangle," as Reuleaux called it, has a constant width...just like a circle. It would certainly work as a manhole cover.

In fact, you can make a manhole cover out of any shape with an odd number of sides. Beginning with a five-sided shape called a pentagon, for example, you can construct a rounded pentagonal shape that has a constant width.

No, I didn't know this information earlier, and not even came close to think about it when I was asked this question. I obtained this information from here.

Love is blind, but marriage is a real eye opener.

1. When I point up it's bright, but when I point down it's dark.
What am I?

2.I have a light side and a dark side, and I hold the universe together.
What am I?

3.I have two arms, but fingers none. I have two feet, but cannot run. I carry well, but I have found I carry best with my feet OFF the ground. What am I?

4.11. Find a simple method of solving:
6751X + 3249Y = 26751
3249X + 6751Y = 23249

love will not hurt if it is not hurt by me

I have a light side and a dark side, and I hold the universe together.

Duct tape :)

'Yeah, That's what Jesus would do. Jesus would bomb Afghanistan. Yeah.' - snowlion

I gave you an Excellent vote for this one because it made me laugh out loud. :-)

"God is dead." - Nietzsche, 1882 "Nietzsche is dead." - God, 1900

This post was edited by null on May 07, 2003.

Yes u r right:-)

love will not hurt if it is not hurt by me

1. When I point up it's bright, but when I point down it's dark.
What am I?

A light switch

A simpler solution is that the man was the one who poisoned it.

And yeah, thats what I thought of... it works as well, because no other specifics were given.

"It was not God who created man, but man who created God." --Santa Caserio

This post was edited by Anduril on May 09, 2003.

1.1. Take the number of your fingers multiplied by the number of you toes divided by one half and add it to the number of months in a year. What is the total?
.
2. Kevin is 14 inches taller than George. The difference between Kevin and Richard is two inches less than between Richard and George. Kevin at 6'6" is the tallest. How tall are Richard and George ?

3. A baseball team had just won the championship game and the players wanted to congratulate each other. They began shaking hands, but each player only shook hands with every other player just once. There are, of course, only 9 players on a baseball team. How many times did the players shake hands?

4.Two trains are on a head on collision course. The trains are currently 65 miles apart. The north bound train is traveling at 55 miles per hour and the south bound train is traveling at 80 miles per hour. What is the distance between the trains two minutes before they collide?

love will not hurt if it is not hurt by me

Here's what I got for these...

Take the number of your fingers multiplied by the number of you toes divided by one half and add it to the number of months in a year. What is the total?

1. Depends on whether or not you count thumbs as fingers... if not, then it is 8*10*2+12 = 172; if you do, then it is 10*10*2+12 = 212. Note that dividing by 1/2 is the same as multiplying by 2

Kevin is 14 inches taller than George. The difference between Kevin and Richard is two inches less than between Richard and George. Kevin at 6'6" is the tallest. How tall are Richard and George ?

2. Kevin is 6'6", Richard is 6'0", and George is 5'4"

A baseball team had just won the championship game and the players wanted to congratulate each other. They began shaking hands, but each player only shook hands with every other player just once. There are, of course, only 9 players on a baseball team. How many times did the players shake hands?

3. The first player shakes 8 people's hands, the next one 7 (his handshake with Player 1 has already been counted), then 6, and so on, so it is 8+7+6+5+4+3+2+1 = 36

Two trains are on a head on collision course. The trains are currently 65 miles apart. The north bound train is traveling at 55 miles per hour and the south bound train is traveling at 80 miles per hour. What is the distance between the trains two minutes before they collide?

4. The trains are moving closer to the collision point at a combined speed of 135 mph. So 2 minutes before the collision, they would be 4.5 miles apart (2 mins * 1/60 * 135 mph)

I am sure I missed at least one of these, but those are my best tries.

"It was not God who created man, but man who created God." --Santa Caserio