NTA Abhyas JEE Main2020MathematicsProbabilityPractice
When two dice are thrown n number of times, the probability of getting a doublet atleast once is greater than 80 % and the least value of n is λ , then the value of λ is equal to
Options
- A6
- B7
- C8
- D9
Correct answer
D. 9
Step-by-step solution
Probability of getting a doublet = 6 36 = 1 6 = p (Let) Let, q = 1 - p = 5 6 Probability of getting a doublet atleast once > 4 5 1 - 5 6 n > 4 5 ⇒ 5 6 n < 1 5 ⇒ n ≥ 9