This is the way he arranged them; every dot stands for an unbeliever, and the strokes for believers—thirty altogether.
PUZZLE OF THE THIRTY MEN.
You begin to count from the left, as the captain did, and if you mark out every ninth man you can keep on counting out the ninth men until only upright strokes are left.
From your knowledge of arithmetic, can you tell me the reason of this puzzle?
The Arabs remember the puzzle by some verses in which every dotted letter stands for an unbeliever and those that have no dots stand for Moslems.
You see that even the story of Jonah and the whale is topsy-turvy out in Arabia!