Answer:
400 ft
Step-by-step explanation:
​h(t)= -16t^2 + 160t
The vertex is found at
h = -b/2a  where b is the coefficient of t and a is the coefficient of t^2
  = -160/(2*-16)
  -160/-32
 5
The time where the maximum occurs is at t=5
To find the maximum substitute into the function
h(5) = -16 (5)^2 +160*5
    = -16*25 +800
    =-400+800
    = 400
The maximum height is 400 ft