JEE Main202125 Jul 2021Evening ShiftMathematicsProbabilityActual
Let X be a random variable such that the probability function of a distribution is given by P X = 0 = 1 2 , P X = j = 1 3 j j = 1 , 2 , 3 , … , ∞ . Then the mean of the distribution and P ( X is positive and even ) respectively, are:
Options
- A3 8 and 1 8
- B3 4 and 1 8
- C3 4 and 1 9
- D3 4 and 1 16
Correct answer
B. 3 4 and 1 8
Step-by-step solution
We have, P X = 0 = 1 2 , P X = j = 1 3 j j = 1 , 2 , 3 , … , ∞ Mean = Σ X i P i = ∑ r = 0 ∞ r · 1 3 r = 3 4 P ( X is even) = 1 3 2 + 1 3 4 + … ∞ = 1 9 1 - 1 9 = 1 9 8 9 = 1 8 .