JEE Main On 8 April 2017 Question 14
Question: An unbiased coin is tossed eight times. The probability of obtaining at least one head and at least one tails is: [JEE Online 08-04-2017]
Options:
A) $ \frac{127}{128} $
B) $ \frac{63}{64} $
C) $ \frac{255}{256} $
D) $ \frac{1}{2} $
Show Answer
Answer:
Correct Answer: A
Solution:
$ 1-\int _{{}}^{{}}{P(All,Head)+P(All,Tail)} $
$ 1={ \frac{1}{2^{8}}+\frac{1}{2^{8}} } $
$ =1-\frac{1}{2^{7}} $
$ =1-\frac{1}{128}=\frac{127}{128} $
