What is the air temperature outside the plane if the flight altitude is 9 km, and the temperature of the earth’s surface is plus 25.

It is known that with an increase in altitude by 1 kilometer, the air temperature decreases by 6 ° С.

In this case, the difference in air temperature between the surface of the earth and outside the aircraft will be:

9 * 6 = 54 ° C.

To find the air temperature outside the aircraft, it is necessary to subtract the previously found temperature difference from the air temperature on the earth’s surface.

Will be:

25 – 54 = -29 ° C.

Answer: The air temperature outside the aircraft is -29 ° C.