Four letters are picked at random from the word THURSDAY. What is the probability that there is at least one vowel among the letters?

Question

Four letters are picked at random from the word THURSDAY.  What is the probability that there is at least one vowel among the letters?

Tom K. · Accepted Answer

Whenever you see the probability of at least one, calculate 1 - the probability of 0.

There are 2 vowels out of 8, so 6 non-vowels.

Then, as we select 4 letters,

1 - C(6,4)/C(8,4) = 1 - 15/70 = 1 - 3/14 = 11/14

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