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October Monthly Contest

Zhang Charles的相片
October Monthly Contest
Zhang Charles發表於2020年 10月 7日(Wed) 16:48
Question 9 says Scott arrives between 1pm and 2pm, but the solution says that Scott arrives between 12pm and 1pm.  Should not the figure be a 2 by 2 square in which 3/8 of the figure is shaded?

Also: Even if Scott arrived at 12pm to 1pm, should not the answer be 25, since the diagram given shows the area in which Mike arrives after Scott?

Lensmire John的相片
Re: October Monthly Contest
Lensmire John發表於2020年 10月 7日(Wed) 18:29

Thanks for pointing this out!

The diagram and solution have been updated to better reflect the actual situation. It is a 1 by 2 square, but it needs to be drawn differently to reflect that Scott can arrive between 1pm and 2pm while Mike arrives between 12pm and 2pm.

In the 2 by 2 square you're thinking of, the bottom half is impossible (as that would be Scott arriving before 1pm), so that does not count towards the probability.

Hope you can see the updated picture and let us know if this helps!