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probabilty

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probabilty

by nidhis.1408 » Tue Oct 16, 2012 8:29 am
leila is playing a carnival game in which she is given 4 chances to throw a ball through a hoop. If her chance of success on each throw is 1/5, what is the chance that she will succeed on at least 3 of the throws?

A. 1/5^4
B. 1/5^3
C. 6/5^4
D. 13/5^4
E. 17/5^4
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by siddhantlife » Tue Oct 16, 2012 8:41 am
leila is playing a carnival game in which she is given 4 chances to throw a ball through a hoop. If her chance of success on each throw is 1/5, what is the chance that she will succeed on at least 3 of the throws?
The answer is B.
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by nidhis.1408 » Tue Oct 16, 2012 8:56 am
The answer is E

p= 3C4*(1/5)^3*4/5+(1/5)^4= 4*1/5^3*4/5+1/5^4
17/5^4
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by anuprajan5 » Tue Oct 16, 2012 9:36 am
My answer to this is based on 2 cases

Case 1: Leila will succeed exactly 3 out of the 4 times

= 1/5*1/5*1/5*4/5*4 = 16/5

The reason why I multiplied the above by 4 is because the possibility that Leila loses on one chance could be any one of the 4 throws

Case 2: Leila will succed on all 4 throws

= (1/5)^4

[spoiler]Case 1+ Case 2 = 17/5^4[/spoiler]
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