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# help

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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?

Jan 22, 2019

#1
+721
-1

$$343_{10}=1000_7$$

So the 4 or 5 must be in the 49's, 7's or 1's place.

There are $$49\times 2=98$$$$7\times 2=14$$ , and $$1\times 2=2$$, so $$98+2+14=114$$.

There are 114 of those integers.

You are very welcome!

:P

Jan 22, 2019