Nerdygeek12
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A spy is trying to open a security door by entering the correct code into a key pad. The key pad has 10 buttons (for the digits 0; 1,........, 9). How many possible codes does she have
to try at most if...
(a) ...she only knows that the correct code is 4 digits long? I got 10!/4!*3!*2!*1!

(b) ...she knows that the correct code consists of 4 distinct digits?

(c) ...she knows which 4 distinct digits are involved in the correct code? I know that this means there are 4! ways of ordering them
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old_engineer
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Duplicate thread.
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