I recall seeing a clever method to estimate the area of an irregular shape. It involved probabilities/ratios/proportions and superimposing the shape onto a 10x10 grid (area=100).
You then randomly scatter 100 pebbles/grains of sand/etc over the grid and see what percentage fall inside the shape. The area of the shape is a percentage of the total area of 100 (the percentage of pebbles that fell inside the shape)..
Is there a better explanation of this concept somewhere? Does it use a grid/area of surrounding area? Was the example best explained with pebbles or sand or something else?