physics
posted by mc .
A projectile fired vertically up from a cannon rises 200 m before returning to the ground. If the same cannon were to fire the same projectile at an angle 45 degrees, then the maximum range would be m.

When fired straight up, the height attained is
H = V^2/(2g)
When fired at at angle A, the range is
R = (V^2/g)sin(2A)
When the angle is 45 degrees, R = V^2/g
and R = 2 H. (The H refers to the straightup value)
Therefore the answer is 400 m.