Expert: Paul Klarreich - 1/31/2010

Question
QUESTION: A fair coin is tossed 7 times.What is the probability to get three tailes before a head is encountered..

ANSWER: Questioner: vaishali
Country: India
Category: Advanced Math
Private: No
Subject: probability
Question: A fair coin is tossed 7 times.What is the probability to get three tailes before a head is encountered..
................................
The usual way to handle probability questions is to rephrase them. As in:

A coin is tossed.

What is the probability that the first three tosses are all tails?

Does that do it?


---------- FOLLOW-UP ----------

QUESTION: Actually I am a bit weak in probability...if you can explain it by solving that will be a great help...thnx in advance..

Answer
Questioner: vaishali
Country: India
Category: Advanced Math
Private: No
Subject: Probability
Question: QUESTION: A fair coin is tossed 7 times.What is the probability to get three tailes before a head is encountered..

ANSWER: Questioner: vaishali
Country: India
Category: Advanced Math
Private: No
Subject: probability
Question: A fair coin is tossed 7 times.What is the probability to get three tailes before a head is encountered..
................................
The usual way to handle probability questions is to rephrase them. As in:

A coin is tossed.

What is the probability that the first three tosses are all tails?

Does that do it?


---------- FOLLOW-UP ----------

QUESTION: Actually I am a bit weak in probability...if you can explain it by solving that will be a great help...thnx in advance..

.............................................
IF you toss three times, you must get tails all three times.  Then apply:

1. The probability that a fair coin comes up tails.

2. The multiplication principle:  If multiple events have probabilities p1, p2, ...
then the probability of all occurring is their product.
..............................
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However, for checking purposes, your answer should be  1/8.