Question 1209380
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Answer: <font color=red>6840</font>


Work Shown:
20*19*18 = <font color=red>6840</font>


Explanation: 
Technically it should be called a permutation lock since order matters in a permutation. 
There are 20 choices for the first slot, 19 choices for the next, and 18 choices for the final slot. This countdown is happening since we cannot repeat values.
Multiply those values to get the final answer.
Another way to reach this answer is to use the nPr permutation formula with n = 20 and r = 3.
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