ProbabilityHard
Question
An unbiased coin is tossed n times. Let X denote the number of times head occurs. If P(X = 4), P (X = 5) and P(X = 6) are in AP, then the value of n can be
Options
A.7
B.10
C.12
D.14
Solution
2 nc5 = nc4 + nc6
4 nc5 = n+1c5 + n+1c6
4 nc5 = n+2c6 + nc6
4 .
4 =
⇒ 24 (n - 4) = (n + 2) (b + 1)n = 7, 14
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