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Question 237583: The sum of the digits in the tens place of all two digit whole numbers is
(a) 100 (b) 101 (c) 450 (d) 901 (e) 990
Answer by vleith(2983)   (Show Source):
You can put this solution on YOUR website! There are 10 2 digit numbers that start with 1 (10,11,12...19)
There are 10 2 digit numbers that start with 2 (20,21,...29)
Do this all the way up to the 10 2 digit numbers that start with 9 (90,91...99)
Now sum them
10*1= 10
10*2=20
10*3=30
...
10*9= 90
So you can see that sum is 10 + 20 + 30 + 40 + ...+ 80 + 90
Adding them up, you get 450
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