Establish the time it takes to travel 109 km before attempting to convert it to mph. This is necessary information because kilometers measure distance, a static measurement, while miles per hour measures rate, a dynamic measurement.
For example, a car may travel 109 km in two hours.
Divide 109 by the number of hours it takes to travel the distance to achieve the rate.
For example, dividing 109 km by two, the number of hours required to travel the distance, equals 54.5 km per hour.
Multiply the result, in this case 54.5, times 0.62 because a kilometer equals 0.62 miles.
So 54.5 x 0.62 = 33.79, so 54.5 km per hour equals 33.79 mph.