The rink has a radius of 4 yards.
If he skates around the outsideof the rink, we can assume he is riding across the circumference of the rink.
Then, in one round he skates an equivalent distance to the circumference of the rink.
This circumference C can be calculated as:
where r is the radius.
Then, we can replace r = 4 and calculate C as:
Answer: 25.13 yards.