The formula with 10.9 substituted
miles = 10.9 ÷ 1.609344 = 6.773
The constant is an exact definition, not a rounded factor: the mile is 1.609344 km, the US gallon is 3.785411784 litres and the imperial gallon is 4.54609 litres. The Kilometres to Miles Converter explains where each comes from and gives a longer table.
At a walking pace of 5 km/h, 10.9 km takes about 131 minutes. At an easy running pace of 10 km/h it takes about 65. In metres it is 10,900.
What 10.9 kilometres means in practice
10.9 km is 6.77 miles, a 10K with the walk back to the car included, which is probably why it is searched for. As a cycle commute it is about 30 minutes in traffic.