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# Probability

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1. Hi, so I'm a bit stuck on this question here.

Buses from Organisation A arrive every 10 minutes, and buses from Organisation B arrive every 8 minutes. What is the probability that when I wait at the bus-stop, a bus from Organisation B will arrive before a bus from Organisation A?

So I've spotted a pattern that the buses A and B will be at the stop at the same time every 40 minutes.

If you arrive in between minutes 0-8, 10-16, 20-24 and 30-32 in this cycle then a B bus will arrive before an A bus.

8-10, 16-20, 24-30 are when an A bus will arrive before a B bus.

The last 32-40 is when both an A bus and a B bus will arrive at the 40th minute.

I am unsure if my method is overly complicated because any answers I calculate from this are wrong. Any help?
2. I can't see anything wrong with this. It looks right. 50% was my answer.
3. (Original post by mik1a)
I can't see anything wrong with this. It looks right. 50% was my answer.
That's what I thought as well at one point, but it appears I am wrong to assume the buses will arrive exactly at their scheduled times.

Also, 0.5 is not one of the possible answers. They are:

0, 0.2, 0.4, 0.6, 0.8, 1, It depends on other things
4. That seems like a perfectly reasonable assumption - not even an assumption, as the questions explicitly states it.

Could the question be wrong? 0.4 was my answer for the probability of A before B.
5. bump
bump

Buses from Organisation A arrive every 10 minutes, and buses from Organisation B arrive every 8 minutes. What is the probability that when I wait at the bus-stop, a bus from Organisation B will arrive before a bus from Organisation A?
There appears to be a fair amount missing from this question! Are you told, for example, that buses arrive according to a Poisson process with inter-arrival time either 8 or 10 minutes? And are you told that you arrive at a bus stop at a time that is uniformly distributed? A bit more context would be helpful; where is this question from?

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