science adv maths is not actuary..
actuary is a discipline related to commerce, tho it is heavy math/statistics based...
in a sci(adv math) stream, u will need to major in math and statistics in the bacholar of science.
career option, well, applied math will grant u into fields which algorithms need to be written to solve real life problems, things like modelling, predicting... statistics, contrary to popular belief, is actually alot theoretical based... after graduate, u can find urself in places like ABS, govt sector, private sector ... any places where data need to be collected and analysed...
a further note, a math major can assist in alot of fields... not only in the field of science... for eg, i believe engineering require a certain level of maths... a 2nd yr subject called financial mathematics is also offered to assist those wanting a career in commerce field.
to major in maths n stat:
first yr u do wut ever one does... 12cp of maths, 36 cp of something else
2nd yr do at least 2 maths 2 stat (1 per sem)
3rd yr, u will be able to do major in maths + stat... (noting however, some 3rd topic require prereq from1st/2nd yr... so choose wisely)