The formula with 1.5 substituted
miles = 1.5 ÷ 1.609344 = 0.932
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, 1.5 km takes about 18 minutes. At an easy running pace of 10 km/h it takes about 9. In metres it is 1,500.
What 1.5 kilometres means in practice
1.5 km is the metric mile of athletics: the 1500 metres has been the championship middle-distance event since 1896 because it fitted a 400 m track better than the mile did. It is 93% of a statute mile, and an elite runner covers it in about three and a half minutes.