Question

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A website password can be four letters long. The letters A, B, C, D, E, F, G, and H are the only letters allowed.

What is the probability that a randomly chosen password starts with D followed by E, and doesn't contain the same letter twice?

Enter your answer as a fraction in simplest form

Answer 1

5 ways to select the 1st letter

4 ways to select the 2nd letter

3 ways to select the 3rd letter

2 ways to select the 4th letter

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Total # of ways = 5*4*3*2 = 120 passwords

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Another way to get the answer 5P4 = 5!/(5-4)!

Explanation: