# Example 31

Last updated at May 29, 2018 by Teachoo

Last updated at May 29, 2018 by Teachoo

Transcript

Example 31 If a fair coin is tossed 10 times, find the probability of (i) exactly six heads (ii) at least six heads (iii) at most six heads Let X : Number of heads appearing Coin toss is a Bernoulli trial So, X has a binomial distribution P(X = x) = nCx n = number of coins tosses = 10 p = Probability of head = 1 2 q = 1 p = 1 1 2 = 1 2 Hence, P(X = x) = 10Cx 1 2 1 2 10 P(X = x) = 10Cx 1 2 10 + P(X = x) = 10Cx Probability exactly six heads Probability exactly six heads = P(X = 6) Putting x = 6 in (1) P(X = 6) = 10C6 1 2 10 = 10 ! 10 6 ! 6 ! 1 2 10 = 10 ! 4 ! 6 ! 1 2 10 = 105 512 (ii) Probability appearing at least six heads i.e. P(X 6) P(X 6) = P(X = 6) + P(X = 7) + P(X = 8) + P(X = 9) + P(X = 10) = 10C6 1 2 10 + 10C7 1 2 10 + 10C8 1 2 10 + 10C9 1 2 10 + 10C10 1 2 10 = 1 2 10 (10C6 + 10C7 + 10C8 + 10C9 + 10C10) = 1 2 10 (210 + 120 + 45 + 10 + 1) = 1 2 10 (386) = 193 512 (ii) Probability appearing at most six heads i.e. P(X 6) P(X 6) = P(X = 6) + P(X = 5) + P(X = 4) + P(X = 3) + P(X = 2) + P(X = 1) + P(X = 0) = 10C6 1 2 10 + 10C5 1 2 10 + 10C4 1 2 10 + 10C3 1 2 10 + 10C2 1 2 10 + 10C1 1 2 10 + 10C0 1 2 10 = 1 2 10 (10C6 + 10C5 + 10C4 + 10C3 + 10C2 + 10C1 + 10C0) = 1 2 10 (210 + 252 + 210 + 120 + 45 + 10 + 1) = 1 2 10 (848) = 53 64

Chapter 13 Class 12 Probability

Example 7
Important

Example 6 Important

Ex 13.1, 10 Important

Ex 13.1, 12 Important

Example 11 Important

Ex 13.2, 7 Important

Ex 13.2, 11 Important

Ex 13.2, 14 Important

Example 17 Important

Example 18 Important

Example 20 Important

Example 21 Important

Ex 13.3, 2 Important

Ex 13.3, 4 Important

Ex 13.3, 8 Important

Ex 13.3, 10 Important

Ex 13.3, 12 Important

Ex 13.3, 13 Important

Example 25 Important

Example 26 Important

Example 27 Important

Example 28 Important

Example 29 Important

Ex 13.4, 3 Important

Ex 13.4, 6 Important

Ex 13.4, 11 Important

Ex 13.4, 15 Important

Example 31 Important You are here

Example 32 Important

Ex 13.5, 4 Important

Ex 13.5, 6 Important

Ex 13.5, 10 Important

Ex 13.5, 13 Important

Example 35 Important

Example 36 Important

Misc 6 Important

Misc 9 Important

Misc 11 Important

Misc 13 Important

Misc 16 Important

Class 12

Important Question for exams Class 12

- Chapter 1 Class 12 Relation and Functions
- Chapter 2 Class 12 Inverse Trigonometric Functions
- Chapter 3 Class 12 Matrices
- Chapter 4 Class 12 Determinants
- Chapter 5 Class 12 Continuity and Differentiability
- Chapter 6 Class 12 Application of Derivatives
- Chapter 7 Class 12 Integrals
- Chapter 8 Class 12 Application of Integrals
- Chapter 9 Class 12 Differential Equations
- Chapter 10 Class 12 Vector Algebra
- Chapter 11 Class 12 Three Dimensional Geometry
- Chapter 12 Class 12 Linear Programming
- Chapter 13 Class 12 Probability

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.