The illustration is a prison of sixteen cells. 
The locations of the ten prisoners will be seen. 
The jailer has queer superstitions about odd and even numbers, and he wants to rearrange the ten prisoners so that there shall be as many even rows of men, vertically, horizontally, and diagonally, as possible. 
At present it will be seen, as indicated by the arrows, that there are only twelve such rows of 2 and 4.
The greatest number of such rows that is possible is sixteen
But the jailer only allows four men to be removed to other cells, and informs me that, as the man who is seated in the bottom right-hand corner is infirm, he must not be moved. 

How are we to get those sixteen rows of even numbers under such conditions?

See answer

Math Genius