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dimbulb · 11-19-2003, 06:45 PM

TIO is correct.

When you arrive at the 4th floor, the elevator can be in 1 of 8 positions.

First floor -UP
2nd Floor - UP/DOWN
3rd - Up/Down
4th-up/down
5th-down

if the elevator is on 1st 2nd 3rd floors, it will either be going up, in which case we are done, or going down, only to come up again. so there are 5 states that will result in the next elevator on the 4th floor that goes up.

Then there is also 1 state (4th floor -UP) that gives you the desired result.

so 6 states out of 8. 3/4.
I'm pretty sure of the answer. Both through my own logic and also coz several math professionals confirm it....

The guy who gave this to me was a math professor at Northwestern before he went into finance. I passed this along to my prof, who 'collects' puzzles. i'm pretty sure its correct.

not that a lot of people agreeing makes things correct.. but....

11-19-2003, 06:45 PM	#5 (permalink)
dimbulb Riiiiight........	TIO is correct. When you arrive at the 4th floor, the elevator can be in 1 of 8 positions. First floor -UP 2nd Floor - UP/DOWN 3rd - Up/Down 4th-up/down 5th-down if the elevator is on 1st 2nd 3rd floors, it will either be going up, in which case we are done, or going down, only to come up again. so there are 5 states that will result in the next elevator on the 4th floor that goes up. Then there is also 1 state (4th floor -UP) that gives you the desired result. so 6 states out of 8. 3/4. I'm pretty sure of the answer. Both through my own logic and also coz several math professionals confirm it.... The guy who gave this to me was a math professor at Northwestern before he went into finance. I passed this along to my prof, who 'collects' puzzles. i'm pretty sure its correct. not that a lot of people agreeing makes things correct.. but.... Last edited by dimbulb; 11-19-2003 at 07:13 PM..