Snapping a Plane

        A plane has a span of 12 metres. It was photographed as it was flying directly overhead with a camera with a depth of 12 cm.

In the photo the span of the plane was 8 mm.

Can you tell how high the plane was when it was snapped?

Answer:  

   

 180 Metres: the liner measurements of the object are to the corresponding measurements of the picture as the distance of the object from the lens is to the depth of the camera.

Let X is the height of the plane. In maters. Then we come to the following proportion:

12000:  8 = X: 0, 12

X = 180 metres