Question 392527
Relative to the first car, the second car (the faster one) travels 16 mph. It takes 4.5 hours to cover a displacement of 72 miles (since 72/16 = 4.5), so 4.5 hours.


The standard way simply uses a bit of elementary algebra. At some time t, 30t and 46t will be separated by 72 miles. Therefore,


46t - 30t = 72 mi


16t = 72


t = 4.5 hr