For projectile on a plane inclined at angle alpha:

Set axes along and perpendicular to the incline:

• Along incline: $a_x$' = -g*sin(alpha) [deceleration going up]
• Perpendicular to incline: $a_y$' = -g*cos(alpha)

If launched at angle beta to the incline with speed u:

• $u_x$' = ucos(beta), $u_y$' = usin(beta)
• Time of flight: T = 2u*sin$\frac{beta}{(g*cos(alpha)}$)
• Range along incline: R = 2$u^2$*sin(beta)*cos$\frac{alpha+beta}{(g*cos^2(alpha)}$)
• Max range when beta = (pi/4 - alpha/2), i.e., bisect angle between incline and vertical

JEE trick: Range up the incline != range down the incline for the same launch angle.