Probability

2008-03-25 9:34 pm

http://upload.ysk.cc/upload/photo/200803-1206180374-EHIXfksy04.jpg

(a) Find the probability that a player can get the bookmarks.

(b) If the game stall owner expects the probability of any player winning the bookmarks to be 1/3, what is the distance (in cm) between any two parallel lines should be
changed to?

(c) In order to make the game more attractive, a player is allowed to throw another CD of diameter 6 cm but the distance between any two parallel lines is kept at 16m. If the CD of diameter 6 cm lies between two parallel lines, the player hets 3 bookmarks, otherwise he/she gets nothing. Nelson wants to get as many bookmarks as possible, which CD ( the one of the diameter 6 cm or that of diameter 12 cm ) should he choose to throw?

回答 (1)

魏王將張遼

2008-03-25 9:56 pm

✔ 最佳答案

(a) With reference to the diagram below:

圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Mar08/Steve1.jpg

Therefore the probability of getting bookmarks = 1/4
(b) Using the above diagram again, if the region between the dotted lines has a width of 6 cm, then the probability will be 1/3, i.e. the distance between any 2 parallel lines should be 18 cm.
(3) Again, from the diagram of (a) through similar approach, we can find out that, when the disc diameter is 6 cm, the probability of winning will become 5/8.
So the expected no. of bookmarks of throwing:
A 12 cm disc = 7 x 1/4 = 7/4
A 6 cm disc = 3 x 5/8 = 15/8
Therefore he should choose to throw the 6 cm ones.

參考: My Maths knowledge

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