SOLUTION: A fair coin is tossed until a head appears.The probability that 3 throws are necessary. I considered 1/2*1/2*1/2=1/8 But the answer is 1/2*1/2 only=1/4. Please suggest.

SOLUTION: A fair coin is tossed until a head appears.The probability that 3 throws are necessary. I considered 1/21/21/2=1/8 But the answer is 1/2*1/2 only=1/4. Please suggest.

Question 674253: A fair coin is tossed until a head appears.The probability that 3 throws are necessary.
I considered 1/2*1/2*1/2=1/8
But the answer is 1/2*1/2 DISABLED_event_only= 1/4.
Please suggest.
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!

 

Hi

consider the sample space: 

P(3 throws necessary) = 1-6/8 = 2/8 = 1/4

THT

THH 

HHH

HHT

HTH

HTT



TTT

TTH



 

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