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# I drop a rubic cube on a carpet and it lands on one of it's

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Manager
Joined: 12 Mar 2003
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I drop a rubic cube on a carpet and it lands on one of it's [#permalink]  03 Aug 2003, 07:07
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I drop a rubic cube on a carpet and it lands on one of it's corners. The probaility of this happening is 1/40. If I drop the cube 5 times, what is the chance that it will land on its corner 3 times ?

Assume that all sides and corners are the same.

SVP
Joined: 03 Feb 2003
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Assuming that all the corners are the same, the probability of placing the cube three times out of five on the corner is 1/40*1/40*1/40*39/40*39/40*5C3=10*39*39/40^5

three corners, two noncorners, and all possible combinations (3+2)
Intern
Joined: 18 Jul 2003
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Binomail Method can be used:

p1 = probability that the cube lands on a corner = 1/40
p2 = probability that the cube does not land on a corner = 39/40

P = 5C3 (p1)^3 (p2)^2

This is the same as the answer given by Stolyar
Intern
Joined: 01 Aug 2003
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I still cant understand the expln. Can someone pls explain it again - and not with Binomial Dist. I dont know what B.D. means!
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