Question 144654
I assume that he may not press the same button twice.
Since order is important permutations apply.
P=n!/(n-r)!
=5!/(5-3)!
=(5*4*3*2!)/2!
=5*4*3
=60 possible ways to press 3 of the 5 buttons in the correct order.
chance of pressing the 3 buttons in the correct order the 1st time: 1/60
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Ed