+81 Let $S$ be the set of all positive integers that have four digits in base $2$. What is the sum of all of the elements in $S$, when expressed in base $2$ ?
+36916 There are 24 = 16 POSSIBLE four-digit numbers in base 2 ....if you can have leading zeroes...I will assume you cannot
then the 4 digit2 numbers are 8 9 10 11 12 13 14 15
add all of these numbers = 92
DO YOU know how to convert this number to base2 ?
