find the circumference to see how much of the wheel is touhing the ground
c=2pir
c=2pi1.9
c=2.8pi
2.8pi=distance per 1 rotation
number of rotations per second times 2.8pi=12feet per second
dvide both sides by 2.8pi
number of rorations per second=12/2.8pi
number of roations per second=6/1.4pi
number of roations per second=3/0.7pi
number of roations per second=30/7pi
aprox
number of roations per second=1.364 rotations per second