Selecting a letter of the alphabet: If 3 letters of the alphabet are selected at random, find the probability of getting at least one letter "x". Letters can be used more than once.

Question

My answer was: P(at least 1 "x) = 1 - (25/26)^3 = 1951/17576 or 0.11

Is this correct?

Answer 1

Most problems of the "at least" type are best done by subtracting from total.

P(at least one x) = 1 - P(no x's) = 1 - (25/26)^3 = 0.111 (3dp)

So, Yes, you are correct.