If a car drives from a to B at a speed of 60km / h, and it returns from B to a at a speed of 40km / h, what is the average speed of the car How many km / h

If a car drives from a to B at a speed of 60km / h, and it returns from B to a at a speed of 40km / h, what is the average speed of the car How many km / h

Let the distance between AB and ab be "1"
Then the time from a to B is 1 / 60 hour
The time taken to return from B to a is 1 / 40 hour
(1 + 1) / (1 / 60 + 1 / 40) = 48km / h

A and B drive from a and B at the same time. A travels 75KM per hour and B 65km per hour. After the first meeting, a and B continue to drive

Let AB be x km away from each other
3X/(75+65)=6
3X=840
X = 280 km

Party A and Party B start from two places 120km apart at the same time. Party B is in front of Party A, 60km an hour for Party A and 40km an hour for Party B. how long does it take for Party A to catch up with Party B

Let a catch up with B after X hours
60X-40X=120
20X=120
X=6
A: six hours later, a overtakes B