So here are the given
information:
4 x 10^6 people
1.97 people = 1 household
16.1 households = 1 piano
1 piano = 1 tuning/year
1 tuner = 3 tunings/working day
1 year = 250 working
days
Multiplying everything:
4 x 10^6 people x (1 household/1.97 people) x (1 piano/16.1
households) = 126115.33 pianos in NYC
126115.33 pianos x (1 (tuning/year)/1 piano) x (1 year/250
working days) x (1 working day/3 pianos/tuner) = 168.15 tuners
Therefore about 168 piano tuners in NYC.