What is the average of all positive integers that have four digits when written in base 3, but two digits when written in base 5? Write your answer in base 10.
Guest #1 is exactly right! Based on that, there 54 numbers from 27 to 80 inclusive that have 4 digits in base 3 and 3 digits in base 5. Their sum in base 10 =2,889. So, the average is: 2,889 / 54 =53.50 in base 10.
