Answer:
 (a)  5 seconds
Step-by-step explanation:
You want to know the hang time of a model rocket launched at 48 ft/s upward from a height of 160 ft.
Time
The time it takes for the rocket to hit the ground is the positive solution to the equation ...
 h(t) = 0
Filling in the expression for h(t), this is ...
 -16t² +48t +160 = 0
 t² -3t -10 = 0 . . . . . . . . . divide by -16
 (t -5)(t +2) = 0 . . . . . . . . factor
The solutions make the factors zero: t = 5, t = -2. We want the positive solution: t = 5.
The rocket will take 5 seconds to reach the ground.
