Looking at my FSI book there isn't any math questions in it, but i can't remember for sure or not if there were any on the test. I would say just freshen up on your basic math. The book is broken down into sections Fire Chemistry, Tool and equipment, Homeland Secuity, Emergency medical technician, and standard operating procedures. I wish i could say you didn't have to buy the book but the fact is you'll have to. In the SOP section they will ask you specific questions related to the fictitional department that is in the book. The main part of the whole test is to see how well and how much you prepaired for the test. They want people who will know the book inside and out.
As for how many questions there are it varried the 3 times i've taken it. Anywhere from 125-150 questions.
Where are you taking the FSI test at?