A car moves with a speed of 30 km/h–1 for half an hour, 25 km/h–1 for one hour and 40 km/h–1 for two hours. Calculate the average speed of the car.

The average speed of the car is 34.28 km/h

Explanation:

We have,

A car moves with a speed of 30 km/h for half an hour, 25 km/h for one hour and 40 km/h for two hours.        

It is required to find the average speed of the car. It is equal to the total distance covered divided by total time taken.

Distance covered for half an hour is,

Distance covered for one hour is,

Distance covered for two hours is,

Total distance is : 15 km + 25 km + 80 km = 120 km

Total time taken : 0.5 h + 1 h + 2 h = 3.5 h

Average speed :

So, the average speed of the car is 34.28 km/h

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.