Answer: 525 mi/hr
Step-by-step explanation:
Let the speed of the faster plane be x miles per hour
Since we know both planes left St. Louis at the same time, we also know that after 4hours they are 700mi apart, and by definition we know that:
Eq(1): Distance = Velocity * Time <=> d = Vt
Also we know that the slower plane traveled at 350 mi/hr thus plugging all known values in Eq(1) for the Slowest plane we obtain the distance covered in 4 hours as follow:
d = Vt <=> d = 350 * 4 <=> d = 1400miles
We also know that after 4 hours the planes are 700mil apart.
Thus the Fastest plane has covered a distance as
1400mil + 700mil = 2100mil
Finally recalling Eq(1) again but now for the faster plane, we now kow the distance and the time thus:
d = Vt <=> V = d/t <=> V = 2100/4 <=> V = 525 mi /hr is the speed of the faster plane.
