How much does "one hundredth" add to "ninety-nine hundredth"?

How much does "one hundredth" add to "ninety-nine hundredth"?

1/100+2/100+3/100+…… 98/100+99/100
=1/100*(1+2+3+4+5…… +98+99)
=1/100*(1+99)*99/2
=1/100*4950
=49.5