What is the sum of all 3 digit positive integers that can be formed using the digits 1, 3, and 7, if the digits are allowed to repeat within a number? Pick:
A) 8,434  B) 9,656  C) 10,989  D) 11,323  E) 12,878
The number of these 3-digit numbers is   3*3*3= 
<gadget id="calculator">  3*3*3</gadget>
<output>27</output>
27   Each digit 1, 3, and 7 will appear in the ones, tens, and hundreds place 9 times each.   The sum equals 9(111) + 9(333) + 9(777)= 10,989   The answer is 10,989.
<result>C</result>
What is the sum of all 3 digit positive integers that can be formed using the digits 1, 3, and 7, if the digits are allowed to repeat within a number?