Question

A child rolls a ball on a level floor 4.0 m to another child. if the ball makes 10.0 revolutions, what is its diameter?

Answer 1

4 m = distance 
You know that each revolution would be equal to the circumference of the ball.
Circumference = Pi * Diameter 
where pi = 3.142 
So then 4 m divided by 10 Revolution will tell us what one revolution equaled. 
In this case 4/10= 0.4This is are circumference, 0.4 = 3.142*d
0.742625716 would be the diameter or 74.26 millimeters.

Answer 2

Circumference : 4/10=0.4m 
Since diameter = circumference / pi (3.14) 
d = 0.4/pi = 0.127388m  
So your answer is 0.127388m