gmihir wrote:

A fair coin is tossed 4 times. What is the probability of getting at least 2 tails?

A. 1/16

B. 1/2

C. 3/16

D. 11/16

E. 3/8

Here's another approach that I used:

Total possibilities = 2^4= 16 since each toss leads to 2 outcomes.

Way of getting no tail in 4 tosses = 1 (H H H H)

Way of getting 1 tail in 4 tosses = 4 (T H H H) (H T H H) ( H H T H) (H H H T)

So ways of getting at least two tails in 4 tosses = 11 (16-5)

Therefore, the probability = 11/16 (D).

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