The answer the i keep getting for this question is way off of the one in book. Can anyone tell me what i am doing wrong??

for each geometric series, find the indicated partial sum

100+300+900+..... Find S11

here's what I did:

Sn=a(r^n-1)/ r-1

a=100 r=3 n=11

S11=100(3^11-1)/11-1

=100(177146)/10

=17714600/10

=1771460

The answer in the back of the book is:

8857300

What?