airspeed of an unladen European swallow in furlongs per fortnight
Google also provides top-ranked sites where this is calculated, but W|A gives a definite answer along with assumptions.
However, changing the query to "airspeed of an unladen African swallow in furlongs per fortnight" returns this:
Wolfram|Alpha isn't sure what to do with your input.
there is unfortunately insufficient data to estimate the velocity of an African swallow (even if you specified which of the 47 species of swallow found in Africa you meant)
Hmmmm...
1 + 1 = 3, for large values of 1.