



 
Hi Michael, Think about randomly guessing the combination. For the first digit you have 5 choices and regardless of your choice you have 5 choices for the second digit. Thus you have 5 × 5 = 5^{5} = 25 choices for the first two digits. Finally, whatever choices you have made for the first two digits you have 5 choices for the third digit. Thus in total you have 5 × 5 × 5 = 5^{3} = 125 possible combinations. Penny  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 