posted by Anonymous on .
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.
My answer was: P(at least 1 "x) = 1 - (25/26)^3 = 1951/17576 or 0.11
Is this correct?
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.