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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 1000 are there?

 Sep 28, 2020
 #1
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The lucky numbers are the numbers that end with 6.  So there are 100 of them that are less than 1000.

 Sep 28, 2020
 #2
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There are 400 such numbers beginning with: 2, 4, 6, 8, 12..........and ending  with: 992, 994, 996 and 998.

 Sep 28, 2020

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