A ball thrown with a speed of 100m/s attains a height of 150m calculate the angle of projection
100 sinθ - 9.8t = 0
Now you have t, and
100 sinθ t - 4.9t^2 = 150
Or, I'm sure our physicist friends will supply a handy formula that skips the need to find t. The wikipedia article on Trajectory has such a formula, but I'm too lazy to look it up...