Question 139000
every 15 min. the fast train arrives & waits 4 min. Then 4 min. after the fast train leaves, the local train arrives & waits 3 min. If you arrive at the station at a random time during the rush period, find the probability that the fast train will be waiting and find the probability that no train will be there.

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Draw the picture of a typical 15 minute period.
fast train: there 4 min; not there 11 min
local train: not there 4; there 3 min ; not there 8 min
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P(fast waiting) = 4/15
P(no train there) = 8/15
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Cheers,
Stan H.