— Disculpe, pero ¿podría decirme por qué yo no tengo compañero, mientras que todos los demás lo tienen? — le gritó. — ¿Por qué? ¡Porque éste es un át… - George Gamow

During each short time interval the motion is assumed to proceed with a constant velocity corresponding to that time, and the distance covered is equal to this velocity multiplied by the time interval.

Let us now divide the time interval from o to t into a large number of very short time intervals and draw vertical lines as shown in the figure, thus forming a large number of thin tall rectangles.

Repeating the same argument for each thin rectangle, we come to the conclusion that the total distance covered during the time interval (o,t) is equal to the area of the staircase or, in the limit, to the area of the triangle ABC.