RD Sharma - Mathematics (Volume 2)

Book: RD Sharma - Mathematics (Volume 2)

Chapter: 33. Binomial Distribution

Subject: Maths - Class 12th

Q. No. 8 of MCQ

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Mark the correct alternative in the following:

Let X denote the number of times heads occur in n tosses of a fair coin. If P (X = 4), P(X = 5) and P(X = 6) are in AP; the value of n is




P(x=r)= nCr pr qn

P(x=4)= nC4 p4 qn-4 = nC4 pn

P(x=5)= nC5 p5 qn-5 = nC5 pn

P(x=6)= nC6 p6 qn-6 = nC6 pn

Since they are in AP;



2 p(x=5) = p(x=4)+ p(x=5)

2nC5 pn = nC4 pn +nC6 pn

4n – 16 = 55n – 225

51n = 209

n= 4

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