If an airplane passes directly over your head at an altitude of 12 kilometers, how

20 kilometres

Step-by-step explanation:

We will imagine a triangle. The hypotenuse of the triangle is the distance between you and the plane. 16 kilometres is the aerial space between you two, in other words its the base of the triangle. 12 km is the length of the third leg of the triangle. We will apply the pythagorean theorem to find the length of the hypotenuse and the distance between you and the plane.

a^2 + b^2 = c^2

12^2 + 16^2 = c^2

144 + 256 = c^2

400 = c^2

square root of 400 is c which equals 20 km.