Question 569224
A student drives the 100 mi trip back to campus after spring break and travels with an average speed of 54 mi/h for 1 hour and 30 minutes.
 There are three parts
: 
  the first part asks for the distance traveled during this time in miles.
   Dist = speed * time
   d = 54(1.5)
   d = 81 mi
;
  The second one says that the traffic get heavier on  the last part of the trip 
so it takes another half-hour and it wants to know the average speed of this leg of the trip (mi/h.
  Speed = dist/time
  time = .5 hr; dist: 100 - 81 = 19 mi
  S = {{{19/.5)}}}
  S = 38 mph speed on the last part of the trip
:
 The final part asks for the final average speed for the total trip (mi/h).
Let a = average speed,  total time: 1.5 + .5 = 2hrs
Write a time equation: time = dist/speed
1.5 + .5 = {{{100/a}}}
2.0 = 100/a
2a = 100
a = 100/2
a = 50 mph was the average speed for the whole trip