Answer:
0.64 seconds
Step-by-step explanation:
In the equation provided:
h = −16t2 + 4t + 4
h is the height of the ball and t is time. Since we want to find the time when the ball touches the floor, then height is 0. This leaves us with the equation
-16
+ 4t + 4 = 0
This is a quadratic equation can be solved with the following formula:

where a=-16
b=4
c=4
Solving for t we will find two different results:


Since time can't be negative, we discard t2 and choose t1.
Since it is required to answer in the nearest hundredth, we round the result to t=0.64 seconds.
To find the time at which both balls are at the same height, set the equations equal to each other then solve for t.
h = -16t^2 + 56t
h = -16t^2 + 156t - 248
-16t^2 + 56t = -16t^2 + 156t - 248
You can cancel out the -16t^2's to get
56t = 156t - 248
=> 0 = 100t - 248
=> 248 = 100t
=> 2.48 = t
Using this time value, plug into either equation to find the height.
h = 16(2.48)^2 + 56(2.48)
Final answer:
h = 40.4736
Hope I helped :)