Answer:
24
Step-by-step explanation:
Well I'm not sure, but if I understand it right, the answer should be 24ms-1, downwards.
Well in short,
Since you're going down at 20ms-1 holding the ball in your hand, that means the ball is also falling at 20ms-1 right? Make sense right? Ya
Cuz i thing in motion stays in motion unless a force is acted upon it
So let's say the person just let go of the ball, it will be 20m/s, but since the question said he threw it with a speed of 4m/s, that means the speed is
20 +4 = 24m/s