Questions
A 2n digit number starts with 2 and all its digits are prime, then the probability that the sum of any two consecutive digits of the number is prime is
detailed solution
Correct option is A
The prime digits are 2, 3, 5, 7. If we fix 2 at first place, then other 2n - 1 places are filled by all four digits. So the total number of cases is 42n-1.Now, sum of 2 consecutive digits is prime when consecutive digits are (2,3) or (2, 5).Then 2 will be fixed at all alternative places.So favorable number of cases is 2n. Therefore, probability is2n42n−1=2n2−4n+2=222−3n=423nTalk to our academic expert!
Similar Questions
A bag contains 10 different balls. Five balls are drawn simultaneously and then replaced and then seven balls are drawn. If the probability that exactly three balls are common to the two draws is p, then the value of 8p is ________.
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