29 vehicles/$km^2$ means (1/29) $km^2$/(1 vehicle)
Per 100 vehicles there are 1/2900 $km^2$.
Whatever you sq kilometers are you have to divide by 100 moto vehicles
100/29 $km^2$/100 vehicles
(100/29)/100=1/29
Why is the wrong?
The other way is if you have more vehicles, you add up the $km^2$ each has, so you multiple (1/29) by 100.