If the acceleration is reduced to 48 km / h in 5 seconds, what is the average acceleration of deceleration linear motion? What is the annoying direction of acceleration?

If the acceleration is reduced to 48 km / h in 5 seconds, what is the average acceleration of deceleration linear motion? What is the annoying direction of acceleration?

120km/h = 120000/3600= 100/3m/s
48km/h = 48000/3600=40/3m/s
Acceleration = (40 / 3-100 / 3) / 5 = - 4m / S
The direction of acceleration is opposite to that of velocity

The two cars leave from two places at the same time and meet in three hours. The speed ratio of car a and car B is 5:4. The distance between the two places is 270 km. What's the speed of the two cars?
This is a question in unit 3 of Volume 1 of grade 6 of pep. Which brothers and sisters can do it? Please, you'd better have the answer the next day! I don't have any reward,

270/3=90
90/(5+4)=10
10*5=50
10*4=40
The speed of the two cars is 50 km / h and 40 km / h respectively

The two cars leave from two places at the same time and meet each other in three hours. The speed ratio of car a and car B is 5:4, and the distance between the two places is 270km

270 △ 3 = 90 (km), 5 + 4 = 9, 90 × 59 = 50 (km), 90 × 49 = 40 (km). A: the speed of car a is 50 km / h, and that of car B is 40 km / h

The speed of a passenger car is 90km / h, and that of a freight car is 60km / h. The freight car is 140m longer than the passenger car
The speed of a passenger car is 90km / h, and that of a freight car is 60km / h. The freight car is 140m longer than the passenger car. If two cars are running in the same direction on the parallel track, and the passenger car catches up with the freight car from behind, the time for them to cross is 1min, and the length of the passenger car is calculated. If the two cars are running in the opposite direction on the parallel track, what is the time for them to cross? The linear equation with one variable is used to solve the problem

The length of the bus is x meters;
If two cars are running in the same direction on the parallel track, it takes one minute for the bus to catch up with the truck from behind,
In this one minute period, the bus has traveled x + 140 meters more than the truck,
90 / 60 km per minute for passenger cars = 1500 m, 60 / 60 km per minute for freight cars = 1000 m,
Countable equation: x + 140 = 1500-1000,
The solution is: x = 360,
That is: the length of the bus is 360 meters;
Let the crossing time be y hours,
In this y-hour period, the passenger cars and trucks traveled 140 + 360 meters = 0.5 kilometers,
The countable equation is 90Y + 60y = 0.5,
The solution is y = 1 / 300,
That is: if the two vehicles are running opposite each other on parallel tracks, their crossing time is 1 / 300 hours = 0.2 minutes = 12 seconds