can someone help me!!!!! i've been stuck in this problem for hours now!!! ack!!!! heeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeelp meeeeeeeeeeeeeeeeeeeeeeee pleeeeeeeeeeeeeeeeeeease!!!!!

question:
the manager of a movie theater determines that the average time moviegoers wait in line to buy a ticket for this week's film is 10 minutes and the average time they wait to buy popcorn is 5 minutes. assuming that the waiting times are independent, find the probability that a moviegoer waits a total of less than 20 minutes before taking his or her seat.

Are you given the standard deviation of waiting times, or the type of distribution it follows?

just underneath that question there is a caveat that i hadn't noticed before. it gives a hint to something my statistics book does not cover.

"Hint: assume that both the waiting time X for the ticket purchase and the waiting time Y in the refreshment line are modeled by the exponential probability density functions."

i did a google on such functios but it all looks very complicated. i'm just confused why my statistics book would throw something at me that it doesn't even explain. :(

alright... it took me AAAAAAAAAAAAAAAAALLLLLLLL night but i finally got it figured out thanks to wikipedia!!!!

i got an answer of 76% so it better be right!!!!

Sounds like a reasonable answer, but I'll have to dust off my Operations Research notes from grad school to double-check it.:D