The formula with 2.4 substituted
miles = 2.4 ÷ 1.609344 = 1.491
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, 2.4 km takes about 29 minutes. At an easy running pace of 10 km/h it takes about 14. In metres it is 2,400.
What 2.4 kilometres means in practice
2.4 km is looked up more than almost any other value on this site because it is the metric statement of the 1.5 mile run used in the US Air Force, Navy and many police fitness assessments; the exact figure is 2.414 km. Six laps of a 400 m track is 2.4 km on the nose.