# propability, train stop

• Dec 6th 2011, 03:08 AM
stevetall
propability, train stop
Hi

I am sorry, I have to make a correction on this opening mail;

There are 5 train stops and 2 passengers. What is propability that EITHER ONE DOES NOT get off
on first two stops ( stop 1 and stop 2 ) ?

- My solution is 1/5^2 + 1/5^2 = 2/25

And propability that both passengers DO NOT get off
on first three stops ( stop 1, stop 2, stop 3 ) ?

- My solution is 1/5^2 + 1/5^2 + 1/5^2 = 3/25

I don't know are my solutions correct?
• Dec 6th 2011, 03:25 AM
Plato
Re: propability, train stop
Quote:

Originally Posted by stevetall
There are 5 train stops and 2 passengers. What is propability that both passengers DO NOT get off
on first two stops ( stop 1 and stop 2 ) ?

Does that mean that both do not get off at stop 1 and both do not get off at stop 2?
In other words the one could at 1 and the other at 2, but just not both at 1 or 2?
• Dec 6th 2011, 04:06 AM
stevetall
Re: propability, train stop
I see. Then it must be;
propability that both passengers DO NOT get off
on first two stops ( stop 1 AND stop 2 ) ?

- 1/5^2 = 1/25
• Dec 6th 2011, 04:09 AM
stevetall
Re: propability, train stop
"Does that mean that both do not get off at stop 1 and both do not get off at stop 2?" - YES

Propability that one can can get off on any stop is clearly 1/5.

And each of those two can get off on any stop he wants. 5 stops and two passengers, indeed.

First I thought 1/5^2 + 1/5^2

But now I think 1/5^2. But don't know...