
There are 4 possibilities of what you might draw
out of the 2 boxes:
 1 mustard and 1 ketchup
 2 mustards
 1 ketchup and 1 mustard
 2 ketchups
In 3 of the 4 possibilities, you'll wind up with
at least 1 mustard. So the chances of picking at
least 1 mustard packet are 3 in 4 or, in another
phrasing, 3 to 1.
Source: Carter, Fulton & Russell,Mighty Mind Boosters,p.170

