# Hope someone help with this probability

• Apr 20th 2009, 09:42 PM
louis1234
Hope someone help with this probability
This is a probability question in some language otherwise than English, I try to translate the meaning into English, and hope someone help.

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If there is a horizontal circular track, where two marbles moving on the track freely and randomly as they are released by the player. The two marbles will finally stop at two places of the track and they will create an angle to the center of the circular track, if the angle created is smaller than or equal to degree 30 , then the player will win \$3, what is the probabilty of he winning \$3

as well as the expected value, what is the expected value of this game?
• Apr 20th 2009, 11:06 PM
The Second Solution
Quote:

Originally Posted by louis1234
This is a probability question in some language otherwise than English, I try to translate the meaning into English, and hope someone help.

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If there is a horizontal circular track, where two marbles moving on the track freely and randomly as they are released by the player. The two marbles will finally stop at two places of the track and they will create an angle to the center of the circular track, if the angle created is smaller than or equal to degree 30 , then the player will win \$3, what is the probabilty of he winning \$3

as well as the expected value, what is the expected value of this game?

I think from symmetry that the probability of the angle being less than 30 degrees will be 30/180 = 1/6.

To get the expected value of the game you need to know how much the player loses if the angle is larger than 30 degrees. Or does the player just get nothing if the angle is larger than 30 degrees?