During a trip, Francine 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? Pick one
A) 12000/x+300 B) (x+60)/4 C) (300-x)/5 D) 600/(115-x) E) 12,000/(x+200)
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>A</result>
During a trip, Francine 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?