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A positive integer k is called a "lucky" number if the units digit of k^6 is 4. How many lucky numbers smaller than 1000 are there?

 
 Oct 11, 2021
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A positive integer k is called a "lucky" number if the units digit of k^6 is 4. How many lucky numbers smaller than 1000 are there?

 

For this to happen the units value of k must be 2 or 8
so, 2,8,12,18, etc

 

1000/10 *2 = 200

 

there will be 200 lucky values of k

 
 Oct 11, 2021

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