A child in a red shirt rides a zip-line while a shirtless child waits on a platform .
Chances are about even that a child rides a zip line while another waits for his turn .
It is almost certain that a child rides a zip line while another waits for his turn .
Chances are about even that a child rides a zip line while another waits for his turn .
A child rides a zip line while another waits for his turn .