Question 45

In a defective 6-faced die with numbers 1 to 6 inscribed, the probability of getting an odd number is twice the probability of getting an even number. Find the probability of getting a 2-digit prime number on 2 successive throws of the die.

Solution

If 'x' is the probability of rolling 2/4/6, then '2x' will be the probability of rolling any odd number

=> x + x + x + 2x + 2x + 2x = 1 => x = 1/9

Two-digit prime numbers that can be formed with 1, 2, 3, 4, 5, 6 are:

11, 13, 23, 31, 41, 53, 61

=> Required probability = 2/9*2/9 + 2/9*2/9 + 1/9*2/9 + 1/9*2/9 + 2/9*2/9 + 1/9*2/9 = 18/81 = 2/9 [No correct option]


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