Three times table is an ABSOLUTE neccessity. Also an ability to divide or multiply by .8 when you move onto turbine powered aircraft. After that, if you're not going on a specific cadet program, then it's a basic understanding of principles thats required.
Also bear in mind that skills needed to pass the theory exams are not normally used on a daily basis. A good example being that you can steer a heading of say, 270 degrees without needing to know that there's 360 of them in a circle. If however you didn't know its 360 degrees all the way round then you'd have a pretty big hole in your knowledge base. As for quadratics, polynomials and other exotic mathematical animals, they're just tools you don't need for deciding on the fuel uplift for the next sector. Simple addition(hopefully error free) to put all th requirements for your company fuel policy though is again an absolute must have.
With the physics side, it's great knowing all the background theory, but again a basic understanding is what's needed. The practicality of understanding why the V speeds are so much higher and the runway sooo much longer at say Johannesburg in the summer than say Birmingham (UK that is) in the winter. This also carries on into the technical side, in that you really just need a good idea of whats in that little box marked Gen 1 on the systems page, and what comes out of it when it's working. Where to get a replacement source of the goodies it supplies if it stops working is a useful thing to know. You don't have to be able to either design the blasted thing or even fix it if it's broke. However the IMPORTANCE of what it's doing for you is again a MUST have.
If you understand the difference of what comes out of the electric sysytem, and why thats different to the water mains, then you're a lot of the way there. Motivation to get the job should provide the necessary urge if you not very scientific, but really want to fly
Having said that, bear in mind what other people have quite rightly said. The higher the qualification you can show a future employer or sponsor, then normally the better.