The GAT this year is on 7 September. You can check out a whole heap of info on the GAT for this year here: https://www.vcaa.vic.edu.au/assessment/vce-assessment/general-achievement-test/Pages/index.aspx.
How are you feeling for it so far? Are you giving it much thought? What do you expect?
how is the gat changing this year?
what level of maths is on the gat? methods, further, specialist??
does the gat affect your overall study score at all
it doesn't impact your study score unless you require a derived study/examination score so basically it is only used if you are unable to attend and complete an exam or there is some sort of disturbance to an ongoing exam
the maths is quite different to the vce maths, it is more about problem solving rather than things you can explicitly prepare for beforehand
