The question is an illustration of selection (or combination)
The number of lock combination is 343
The given parameters are:
<em />
<em> --- the number of digits to select from</em>
<em />
<em> --- the number of digits the lock uses</em>
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Because the digits can be repeated, the number of lock combinations is:

So, we have:


Hence, the number of lock combination is 343
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