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 Question from Rob: If there is a 4 digit passcode with only 6 punch in symbols, how many possibilities are there and what are they? symbols are: Y, X, RB, RT, LB, LT. Please get back to me, thanks for your time and help.

Hi Rob.

It depends on whether duplicates are allowed. For example, is Y, X, LT, X allowed?

It also depends on whether order is important. Is Y, X, LT, RT different from RT, Y, X, LT?

Assuming the answers to both question are Yes, you have 6 choices for each of the four positions, so the number of possibilities is 6 x 6 x 6 x 6.

If duplicates are not allowed, then you have 6 choices for the first symbol, 5 for the next, etc. So the number of possibilities is 6 x 5 x 4 x 3.

If order is not important, you have to weed out duplicates. The number of duplicates is the number of ways of arranging 4 things: 4 x 3 x 2 x 1 . So you would divide the number of possibilities by 24.

Cheers,
Stephen La Rocque.

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