Question 325620
At height 48 feet, -16t^2 + 64t = 48
=> 16t^2 - 64t + 48 = 0
=> t^2 - 4t + 3 = 0
=> t^2 - t - 3t + 3 = 0
=> t(t - 1) - 3(t - 1) = 0
=> (t - 3)(t - 1) = 0
=> t = 3, 1
Hence, the ball is at a height of 48 feet at time 1 sec and 3 sec.
Answer: b