If the speed of a car from Hangzhou to Shaoxing is 60km / h in the first half and 40km / h in the second half, the average speed of the whole journey is ()

t1=(s/2)/60
t2=(s/2)/40
t=t1+t2
The average velocity is = s / T
=48km/h

It takes 7.5 hours for a car to go back and forth from a to B. how many kilometers is the distance between a and B?

It took x hours to get there and Y hours to get back
be
x + y = 7.5
40x = 60y
x = 7.5-y
40(7.5-y) = 60y
300 - 40y = 60y
300 = 100y
y =3
x + 3 = 7.5
x = 4.5
4.5* 40 = 180KM
Therefore, the distance between a and B is 180km

A car full of goods drove from place a to place B at a speed of 40km / h, unloaded the goods and returned along the original road, with an empty speed of 60km / s
Find the average speed of the car,

2/(1/40+1/60)=48km/h

1. A car originally planned to travel 50 kilometers per hour, and it took 7.7 hours to travel from place a to place B. actually, it traveled 110 kilometers in two hours. How many hours does it take to complete the whole journey?
2. A car was originally planned to travel 50 kilometers per hour, and it took 7.7 hours to go from place a to place B. in fact, it traveled 110 kilometers in 2 hours. How many hours less than the plan?
3. A car was originally planned to travel 50 kilometers per hour, and it would take 7.7 hours to go from place a to place B. the actual speed is 10% higher than the plan. How many hours does it take to complete the whole journey?
4. There are two ropes, one is 30 meters long and the other is 24 meters long. After cutting the same length of both, the remaining length of the two wires is 5:3. How long is the cut section?
5. A workshop used to have 78 kg of zinc and copper. Now it needs to add 14 kg of copper to melt and cast copper and zinc into an alloy according to the ratio of 1:3?
(use solution ratio, e.g. several to several = several to x)

1.7 hours 7.7 × 50 = (110 △ 2) x
2.0.7 hours 7.7-7.7 × 50 ^ (110 ^ 2) = x
7 × 50 = [50 + (50 × 10%)] x
15 m (30-x) × 3 = (24-x) × 5
5.9kg copper is x, zinc is y x + y = 783 (x + 14) = y
78-3(X-14)=X

If the speed of a car from Hangzhou to Shaoxing is 60km / h in the first half and 40km / h in the second half, the average speed of the whole journey is ()