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## #1 2017-05-11 23:43:49

Eduardo.juan
Member
Registered: 2017-05-11
Posts: 2

### Spider and ant

A spider and an ant walk along the circular edge of an open cylindrical tank, in opposite directions. They start walking from the same point and the spider walks at a speed of 3/4 rpm (revolutions per minute) while the ant at 2/3 rpm. Sometime between 22 and 23 minutes since they started walking, a
guard standing in the middle point of the tank holds a torch and shines with its beam the edge of the tank, aiming exactly at the point where the two insects had started walking. If the beam has an opening angle of 90o, can you find the probability that the guard sees both insects?

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## #2 2017-05-13 03:48:08

salem_ohio
Member
Registered: 2016-03-11
Posts: 37

### Re: Spider and ant

Eduardo, I guess the question is to find the probability that both insects find themselves in one quarter of the circle and in particular 1/8 before and 1/8 after the starting point, during the minute 22 to 23, right?
So let's start by setting the boundaries for each. Where will the spider be after exactly 22 minutes? and after 23? What about the ant?

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## #3 2017-05-16 17:37:08

salem_ohio
Member
Registered: 2016-03-11
Posts: 37

I got 18.75%.

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