Question

What is the speed of an automobile in kilometers per second if it travels at 30 miles per hour

Answer 1

well you could type
30 mph = km/s
up in your search engine :)

or you could know 1 statute mile = 1.61 km approximately
so
30 miles/hour * 1.61 km/mile * 1 hour/3600 seconds =

BUT more likely you have a typo and it asked for meters/second in which case you would multiply by 1000/3600 instead of 1 / 3600

Answer 2

1 mi = 1 609.344 km

1 h = 3 600 sec

30 ∙ 1 609.344 km / 3 600 sec = 0.0134112 km / s

Answer 3

My typo:

1 mi = 1 609.344 m = 1.609344 km

1 h = 3 600 sec

30 ∙ 1 .609344 km / 3 600 sec = 0.0134112 km / s

Answer 4

What is the speed of an automobile in kilometers per second if it travels at 30 per hour