Question 319424
30 miles at 40 mph
time taken at this speed = 30/40 = 3/4 hours 
..
75 miles at 50mph
time taken = 75/50 = 3/2 hours 
Total time taken = 3/4 +3/2 hours=3+6 /4
=9/4 hours
Total distance traveled = 30+75 = 105 miles
Average speed = 105/  9/4
=105*4/9
46.6 mph is the average speed