I cannot understand how much probability.
If probability equal 1, answer in infinity.

Edited by author 09.03.2009 09:02

You don't have the right to call the problem improper only because you don't understand it!!!
Maybe read the statement more carefully and find out what is the expected time in mathematics.

I think I understend task well and how decide it if we don't think about probability. If we have {2,"ba"} I find the solve is 4.6(6). But monkey can push "bbbbbb" with probability>0. You can answer me to allaksus@rambler.ru .

Actually the probability of typing "bbbbbb..." (infinity times) is 0 although this can happen!
And the answer to {2,"ba"} is exactly 4.

Sorry, I agree with you =4 (I found one error), but the probability this event is 0.6875 . Why it isn't 0.999 or 0.99999.

If I will be audietorium I will be intrest how many maximum time I must wait with probability 0.99

You mustn't find the maximum time but the EXPECTED time, which is equal to 1*P(1) + 2*P(2) + 3*P(3) + 4*P(4) + ...
P(i) is the probability of the situation, where the first appearance of the required word ends at position i.
I don't know how to explain it more clearly.

Edited by author 14.03.2009 01:42

The task doesn't say about condition (EXPECTED time, maximum time, ...) .