A car set out for the mountain area, traveling 42km per hour, and arrived in 6 / 7 hours. It only took 3 / 4 hours to return from the original road (Continued) how many kilometers per hour is the average return time?

(42*6/7) ÷3/4=48
Return is an average of 48 kilometers per hour

Uncle Wang drove from place a to place B. when he started, the speed was one ninth higher than the planned speed. As a result, he drove 1.5 hours ahead of schedule. When he returned, he drove 120 times at the original speed
After 1000 km, increase the speed by 20%, so arrive two hours ahead of time. How many kilometers is the distance between AB and ab. (with one yuan per square!)

∵ the speed is one ninth higher than the planned speed, and the result is 1.5 hours ahead of schedule;
The planning time: 1.5 △ 1 / (1 + 1 / 9)] = 1.5 △ 1 / 10 = 15 hours
Suppose the planned speed is XKM / h, then the distance between AB and ab is 15xkm
120+（1+20%)x·(15-2-120/x)=15x
∴120+18x-2.4x-144=15x
x=40
∴15x=600
A: 600 kilometers

Uncle Wang drove from place a to place B. he planned to travel 84km per hour, which took 5 hours to arrive. In fact, he arrived 1.5 hours ahead of schedule
Q: how many kilometers more per hour than planned?

Let the actual velocity be X
x:84=5:(5-1.5)
3.5x=84×5
x=120
120-84=36
The actual line per hour is 36 kilometers more than the plan

Uncle Wang drives from Wangzhuang at a speed of 40 km / h
It took Uncle Wang 3 hours to drive from Wangzhuang to Lizhuang at the speed of 40 km / h, and 2 hours to return from Lizhuang to Wangzhuang. He asked Uncle Wang for the average speed of driving back and forth from Wangzhuang to Lizhuang

Average speed = total distance / total time
The total distance is two times of the distance from Wangzhuang to Lizhuang, one time for each trip. 40 * 3 is the distance between the two places, but also multiplied by 2
Total time = 3 + 2
The average speed is 40 * 3 * 2 / (3 + 2) = 48 m / h

A car set out for the mountain area, traveling 42km per hour, and arrived in 6 / 7 hours. It only took 3 / 4 hours to return from the original road (Continued) how many kilometers per hour is the average return time?