When the meter is cut in half, so is the tempo. If you take a 4/4 Tango at 120 bpm and cut the meter in half to 2/4, you would also cut the tempo in half to 60 bpm. So while the value of a "quick" may be a quarter note in 4/4 but only an eighth note in 2/4, the actual time value of the quick is the same: Approx 1/2 second.
I hope this makes sense.
Sincerely,
Jonathan Atkinson