JEE Main202127 Aug 2021Morning ShiftMathematicsProbabilityActual
When a certain biased die is rolled, a particular face occurs with probability 1 6 - x and its opposite face occurs with probability 1 6 + x . All other faces occur with probability 1 6 . Note that opposite faces sum to 7 in any die. If 0 < x < 1 6 , and the probability of obtaining total sum = 7 , when such a die is rolled twice, is 13 96 , then the value of x is
Options
- A1 16
- B1 12
- C1 8
- D1 9
Correct answer
C. 1 8
Step-by-step solution
Probability of obtaining total sum 7   = Probability of getting opposite faces. Probability of getting opposite faces = 2 1 6 - x 1 6 + x + 1 6 × 1 6 + 1 6 × 1 6 = 2 1 6 - x 1 6 + x + 1 6 × 1 6 + 1 6 × 1 6 = 13 96 x = 1 8