A because radius is half of the diameter
Answer:

Step-by-step explanation:
Given


Required
How fast is the ball seem to be moving?
This question illustrates relative velocity;
Since the ball and the train moves in the same direction, the required velocity relative to the person standing behind is:

i.e. we add both velocities


For the second one 1 mph equals 1.6 km so i’m pretty sure it would be all of them
6 1/13 for sure
5 14/13 -> 79/13
79/13 to mixed number is 6 1/13
................................ the answer is 1500