Find the area of triangle APB in terms of x, the side of the square.
The Canterbury Puzzles Henry Ernest Dudeney
abbreviation (in the US)
See all-points bulletin
also a.p.b., 1960, police jargon initialism for all-points bulletin, itself attested by 1953 (perhaps more in the jargon of detective novels than in actual police use).
all points bulletin
apca Air Pollution Control Association
apcd Air Pollution Control District
apdim Association of Program Directors in Internal Medicine
apda American Parkinson’s Disease Association