Is oswaal question bank with complete solutions helpful for sa1 maths cbse to gain 90/90.

@meenu 
yes , osswal is a good book to start with , but as far as class 10^th are concerned , then first u have to do ncert each and eevry question alongwith solved examples , 
that is your main textbook and that u have to solve . 
and after that take osswal , even goyal assignments are also good , practice as much ques as u can . 
take trigo., seriously as its the d=foundation now for you . 

ALL THE BEST ..