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some confusing math probablity problems
Posted:
Apr 9, 2014 11:13 PM


hi,
There are a couple of math problems in geometric probablity that we seem to have a problem with. My daughter and I were trying to work this problem out, but the answer we get is different from what the suggested answer is in the book.
P1. A bus comes to a station once every 10 minutes and waits at the station for 1.5 minutes.
question 1. Find the probability that the bus will be at te station when you arrive (Book answer: 0.15)  (our answer 0.13  1.5/11.5) ours is wrong
question 2. IF you go to the station 20 times, predict about how many times you will have to wait less than 3 minutes. (book answer: 9 times)  (our answer which is wrong is: (3/11.5) * 20 = 7.xxx)
P2. A radio station gives a weather report every 15 minutes. Each report lasts 45 seconds. Suppose you turn on the radio at a random time.
Question 1. Find the probability that you will have to wait more than 5 minutes to hear the weather report
Question 2. If you turn on the radio at 50 random times, predict about how many times you will hahve to wait less than 1 minute before the start of the next weather report.
I don't understand how it works obviously. We did other geometric prob problems, but these two are confusing. Please explain your answers. I am a little confused myself. thanks
s



