Answer:
t = 0.995 s, 5.127 s
Step-by-step explanation:
Δx = v₀t + 1/2at²
25.0 m = (30 m/s)t + 1/2(-9.8 m/s²)t²
-4.9t² + 30t - 25 = 0 solve this quadratic equation for t (2 solutions)
t = 0.995 s, 5.127 s
It reaches a height of 25 m in 0.995 s, then again 5.127 s later on its way back down