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

Guest Jan 22, 2019

#1**-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

CoolStuffYT Jan 22, 2019