SOLUTION: What is the sum of the digits in the 99-digit integer formed by listing the numbers 100 through 132 in order?

That's the number
100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132

Its sum of digits in the sum of an arithmetic sequence.  Since 
the number has 99 digits, and each number of the sequence has 
3 digits, the number of terms is . The formula
for the sum of anb arithmetic sequence is:

Sn = (a1 + an)

with n=33, a1=100, an=a20=132

S33 = (a1 + a20)

S33 = (100 + 132)

S33 = (232) = 3828

Edwin