How long will it take the ball to reach the ground

When the ball reaches the ground, its height is 0.
We set the height function equal to zero and solve for t, the time.

h = -16t^2 + 250

-16t^2 + 250 = 0

16t^2 - 250 = 0



   or  

   or  

  or  

We discard the negative solution since time must be positive.
The positive solution is



4.0 seconds