This may be a no-brainer (obvious thruth), but the funny thing is that the more sex you have, the more likely you are to get pregnant. ... If you're a female, of course.
Something that requires (needs) little mental effort or intelligence to perform or understand. The term is often applied to (used for) decisions which are straightforward (clear) or sometimes to people who appear (seem) to lack intelligence.
'No-brainer' is American in origin and was first used there in the 1950s. The earliest example that I've found of its use in the sense of 'requiring little mental effort' is in this 'The Berrys' cartoon, by Carl Grubert, which appeared in the Long Beach Independent, December 1959:
The first example of the term with the meaning of 'easily made decision' is from the Canadian newspaper The Lethbridge Herald, January 1968, in a report on an ice hockey game:
He'd break in on a goalie and the netminder would make one of those saves that our manager-coach, Sid Abel, calls "a no-brainer."
The application of 'no-brainer' to individuals came later, after the term was already well established; for example, this from Tom Alibrandi's 1979 novel Killshot:
"I'll unanimously be voted the no-brainer-of-the-month award."
Wondering What To Do On 'No Brainer Day'?
Today, February 27th, is officially “No Brainer Day,” a day for all of us just to kick back, stop over analyzing every little thing and just have fun with the friends, family and the hobbies we love.
See more at: http://www.allsparkfireworks.com/blog/set-off-fireworks-on-no-brainer-day/