Actually three old well known brainers:
[ol]
[li]Why after protective helmets were introduced for infantry in WWI there was recorded increase of soldiers with head injuries?[/li]
[li]During WWII the British Air Ministry planned to add more armour on the bombers. For that purpose they observed and recorded number and location of bullet holes on returning aircraft, and the goal was to use this information to determine where to best add armor to the plane’s structure. Based on this, the Air Ministry suggested adding armor to wing ends and fuselage sides as those areas had most holes. A smart guy named Abraham Wald said: “Do exactly the opposite! Reinforce the the parts with least number of holes!” Why did Mr.Wald want least hit sides to be reinforced? Was he a German collaborator?[/li]
[li]Why the better Medivac teams work on the frontline the higher the mortality rate in the hospitals?[/li][/ol]
And remember: NO Googling while answering!