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How many of the 343 smallest positive integers written in base 7 use 4 or 5 (or both) as a digit?

 Feb 11, 2018
 #1
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343 in base 10 = 1,000 in base 7

I count 38 fours and 37 fives out of 343_7 numbers. You can count  them yourself by listing them and you will see a pattern: 0,1,2,3,4,5,6......, 10,11,12,13,14,15,16........., 20,21,22,23,24,25,26......, 30,31,32,33,34,35,36.......and so on. Now, you can see the pattern.

 Feb 11, 2018

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