At what altitude does the plane fly if the air temperature is +15 at the surface of the earth and -30 outside the plane?

We know that air temperature decreases with height. For every kilometer, the temperature drops by 6 degrees.

The solution of the problem:

1) Find the temperature difference: +15 – (-30) = 45 degrees;

2) Calculate the altitude at which the plane is flying: 45: 6 = 7.5 kilometers

Answer: the plane is flying at an altitude of 7.5 kilometers.