Take a look at these numbers:
1st number is population, 2nd is area of city (sq.km) and 3rd is density
Mumbai India - 14,350,000...484 ... 29,650
Tokyo Japan - 33,200,000 ... 6,993 ... 4,750 - more people but more land - less density
New York USA - 17,800,000 ... 8,683 ... 2,050
When you compare New York to Mumbai then New York for sure is Low-Density. Even New York compared to Tokyo make New York appear to be Low Density. However if you compare New York to other American Cities then New York may be considered High Density. It is best if you look at the chart and pick a city that you can compare to New York or another well known city.
Go to this site as it has a chart listing 250 world cities. This is where I got the above information. You can then be sure your answer is correct.
http://www.citymayors.com/statistics/largest-cities-density-125.html