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# probability

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Manager
Joined: 08 Nov 2005
Posts: 182
Followers: 1

Kudos [?]: 14 [0], given: 10

probability [#permalink]  29 Sep 2009, 09:02
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Difficulty:

(N/A)

Question Stats:

100% (03:43) correct 0% (00:00) wrong based on 3 sessions
For one toss of a certain coin,the probability that the outcome is heads is 0.6.If this coin is tossed 5 times,which of the following is the probability that the outcome will be heads at least 4 times?

A. (0.6)^5
B. 2(0.6)^4
C. 3(0.6)^4*(0.4)
D. 4(0.6)^4*(0.4)+(0.6)^5
E. 5(0.6)^4*(0.4)+(0.6)^5

Manager
Joined: 14 Dec 2008
Posts: 171
Followers: 1

Kudos [?]: 16 [0], given: 39

Re: probability [#permalink]  29 Sep 2009, 09:32

formula used - ncr(p^r)(q^(n-r))

so p=5c4(0.6^4)(0.4) + 5c5(0.6^5) which is last ans option
Manager
Joined: 14 Dec 2008
Posts: 171
Followers: 1

Kudos [?]: 16 [0], given: 39

Re: probability [#permalink]  29 Sep 2009, 09:33
E. 5(0.6)^4*(0.4)+(0.6)^5
Re: probability   [#permalink] 29 Sep 2009, 09:33
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