A fair coin is tossed 4 times. What is the probability of getting exactly 2 heads?
Show the answer and explanation
Correct answer
B. 3/8
Principle or equation
For repeated independent trials with two outcomes, the probability of exactly k successes in n trials is C(n, k) p^k (1-p)^(n-k).
Why this answer is correct
Here n = 4, k = 2, p = 1/2. Number of favorable sequences: C(4,2) = 6. Total outcomes: 2^4 = 16. Probability = 6/16 = 3/8.
Example
For 3 coin tosses, probability of exactly 2 heads is C(3,2)(1/2)^3 = 3/8.
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