If the horizontal

Where,

R=Normal reaction

θ=Angle of banking

v=velocity of the car

m=mass of the car

g= acceleration due to gravity

r=radius

From the diagram, we can see that

R cosθ = mg

R sinθ = mv²/r

On dividing the above equations, we get

Tanθ = v²/rg

⇒ θ=tan^-1(v²/rg)

We are given, v=10m/s

r=30m

⇒ θ=tan^-1(10×10/30)

⇒ θ=tan^-1(1/3)

∴ Angle of banking should be tan^-1(1/3)