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If only the positive integers from 1 through 49, inclusive, are written on a piece of paper, what is the sum of all the digits that are written on the paper?

 Aug 26, 2018
 #1
avatar+374 
+3
\(1\) \(2\) \(3\) \(4\) \(5\) \(6\) \(7\) \(8\) \(9\) \(1\)\(0\)
\(1\)\(1\) \(1\)\(2\) \(1\)\(3\) \(1\)\(4\) \(1\)\(5\) \(1\)\(6\) \(1\)\(7\) \(1\)\(8\) \(1\)\(9\) \(2\)\(0\)
\(2\)\(1\) \(2\)\(2\) \(2\)\(3\) \(2\)\(4\) \(2\)\(5\) \(2\)\(6\) \(2\)\(7\) \(2\)\(8\) \(2\)\(9\) \(3\)\(0\)
\(3\)\(1\) \(3\)\(2\) \(3\)\(3\) \(3\)\(4\) \(3\)\(5\) \(3\)\(6\) \(3\)\(7\) \(3\)\(8\) \(3\)\(9\) \(4\)\(0\)
\(4\)\(1\) \(4\)\(2\) \(4\)\(3\) \(4\)\(4\) \(4\)\(5\) \(4\)\(6\) \(4\)\(7\) \(4\)\(8\) \(4\)\(9\)  

 

By the chart, you can see that there are:

 

Fifteen \(1\)'s

Fifteen \(2\)'s

Fifteen \(3\)'s

Fifteen \(4\)'s

Five \(5\)'s

Five \(6\)'s

Five \(7\)'s

Five \(8\)'s

Five \(9\)'s    and 

Four \(0\)'s (Of course, the zero's would not matter, because they are asking for the sum).

 

So we are trying to find \(s\), the sum of the digits. We can get the equation \(s = 15(1) + 15(2) + 15(3) + 15(4) + 5(5) + 5(6) + 5(7) + 5(8) + 5(9) \), which is equal to \(s = 15 + 30 + 45 + 60 + 25 + 30 + 35 + 40 + 45\), which we can finally get \(s = 325\)

 

- Daisy

 Aug 26, 2018
 #2
avatar+973 
+1

Thanks Correct!

Lightning  Aug 26, 2018

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