The formula for maximum height is:
H = v²sin²θ/2g
The formula for range is:
R = v²sin(2θ)/g
The relationship between the two is written as:
R = 6H
v²sin(2θ)/g = 6(v²sin²θ/2g)
v²sin(2θ)/g = 3v²sin²θ/g)
Cancelling out like terms,
sin(2θ) = 3sin²θ
Solving for θ using a scientific calculator,
θ = 33.7°