What is the tens' digit T of the sum of the first 40 terms of 1, 11, 111, 1111, 11111, 111111, ...? Choose the correct choice from the following answers:
A) T=2 B) T=3 C) 4 D) 8 E) 9
All of the first 40 terms have 1 at the units place.   Except the first term, the tens digit of all the remaining 39 terms is 1.   So now if you do the addition   1 1   1 1   . . .   . . .   . . .   1 1   0 1   3 0   Answer is T=3
<result>B</result>
What is the tens' digit T of the sum of the first 40 terms of 1, 11, 111, 1111, 11111, 111111, ...?