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joyce
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The probability that the head of a coin comes out is equal 09 Feb 2007, 22:33
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The probability that the head of a coin comes out is equal to that the tail of a coin comes out when it is tossed up once. If a coin is tossed up five times, what is the probability that at least three heads of a coin will come out?

A: 1/4
B: 1/3
C: 1/2
D: 2/3
E: 3/4

OA: C



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prude_sb
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Concentration: Management, Strategy & Finance
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The probability that the head of a coin comes out is equal 09 Feb 2007, 23:10
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(5C3+5C4+5C5)*(1/2)^5 = 16/32 = 1/2
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overtherainbow
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The probability that the head of a coin comes out is equal 02 Apr 2007, 03:31
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we'll take the 1 - approach,

32 outcome of 5 coins.

0 tails = HHHHH 1 outcome
1 tail = HHHHT HHHTH HHTHH HTHHH THHHH or 5C1 5 outcomes
2 tails = 5C2 = 10 outcomes

total outcome of up to 2 tails = 1+5+10 = 16

thus, for at least 3 heads we get

1- (16/32)=16/32 = 0.5
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vijay2001
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The probability that the head of a coin comes out is equal Updated on: 03 Apr 2007, 07:29
Originally posted by vijay2001 on 03 Apr 2007, 06:56.
Last edited by vijay2001 on 03 Apr 2007, 07:29, edited 1 time in total.
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There is a formula for calucating probabilty for repeating events

See attached doc
Attachments

SDOC3320.pdf [28.24 KiB]
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ywilfred
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The probability that the head of a coin comes out is equal 03 Apr 2007, 07:21
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We need at least 3 heads, so the words that we need to arrange are:

HHHTT
HHHHT
HHHHH

Each case has a probability of 1/32

Case 1: HHHTT -> number of combinations = 5!/3!2! = 10. P = 10/32 = 5/16
Case 2: HHHHT -> number of combinations = 5!/4!1! = 5. P = 5/32
Case 3: HHHHH -> only 1 case -> 1/32

Total = 5/16 + 6/32 = 5/16 + 3/16 + 8/16 = 1/2

C
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andrehaui
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The probability that the head of a coin comes out is equal 03 Apr 2007, 11:16
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number of possible cases=10 as C5,3
number of total tentatives=5

so 10/5 = 1/2


is this way of solving correct for you?



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