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A positive integer k is called a "lucky" number if the units digit of k^4 is 6. How many lucky numbers smaller than 10 are there?

 Nov 2, 2022
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A positive integer k is called a "lucky" number if the units digit of k^4 is 6. How many lucky numbers smaller than 10 are there?  

 

14      =            1  

24      =          16  

34      =          81  

44      =        256  

54      =        625  

64      =      1,296  

74      =      2,401  

84      =      4,096  

94      =      6,561            Looks like there are 4 of them.  

.

 Nov 2, 2022

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