During a trip, joe traveled x percent of the total distance at an average speed of 30 miles per hour and the rest of the distance at an average speed of 40 miles per hour. In terms of x, what was Francine's average speed for the entire trip?
Options
A) (180-x)/2
B) (x+60)/4
C) (300-x)/5
D) 600/(115-x)
E) 12000/x+300
total distance =100 ;total time = T   t1 = x/30 t2 = 100-x /40   T =t1+t2 = x/30 + 100-x/40 = (40x + 3000- 30x)/1200   = (10x+3000)/1200   = x+300/120   av speed = 100*120/x+300 = 12000/x+300   12000/x+300
<result>E</result>
During a trip, joe traveled x percent of the total distance at an average speed of 30 miles per hour and the rest of the distance at an average speed of 40 miles per hour. In terms of x, what was Francine's average speed for the entire trip?