Understanding the Conversion:

* 1 kilometer (km) is approximately equal to 0.621371 miles.

* 1 hour (h) is equal to 1 hour.

Calculation:

1. Multiply by the conversion factor: 42 km/h * 0.621371 miles/km = 26.055422 mph

Rounded Result:

42 km/h is approximately equal to 26.06 mph (rounded to two decimal places).