How do I convert 2 units simultaneously

For example if I am asked to convert 58 miles/sec into km/hour how do i go about it? I already know how to convert between single units.. but am lost when it comes to double units

Revised version!

For example if I am asked to convert 58 miles/sec into km/hour how do i go about it? I already know how to convert between single units.. but am lost when it comes to double units
1.609 km = 1 mile
3600 seconds = 1 hour
58 miles/sec * 1.609 km/ mile * 3600 sec/ 1 hour = 335,959.2 km/hr

Let show you the complete English to Metric conversion of the units.
3600 s = 1 hr
1 km = 1000 m
1 m = 100 cm
2.54 cm = 1 inch
12 inches = 1 ft
5280 ft = 1 mile
12 inches = 1 ft

Arrange the units so all units cancel except km
I cancel the lengths first and then the time.

58 m/s * 5280 ft/mi * 12 in/ft * 2.54 cm/in * 1 m/100 cm * 1 km/1000 m * 3600 s/hr = 336,031.0272 km/hr
100 cm and 1000 m are in the denominator, so cm and m will cancel.
This is called unit cancelation!


5280 ft/mi * 12 in/ft * 2.54 cm/in * 1 m/100 cm * 1 km/1000 m = 1.609344 km/mile

The answers differ because 1.609 is the rounded version of 1.609344

You do it in a series of multiplications by factors equal to unity:

58 mi/sec * [1.61 km/mi]*[3600 sec/hr] = 336168 km/hr

Note that miles & seconds cancel, leaving only km & hr.........