Question 2
Let W be the smallest positive integer consisting of only digits 3 and 7 and divisible by both 3 and 7. What is the sum of digits of W?
**Editorial note for this self-study exercise:** Each digit may be 3 or 7; both different digits need not occur. Enter the digit sum, not W.
**Editorial note for this self-study exercise:** Each digit may be 3 or 7; both different digits need not occur. Enter the digit sum, not W.