Given :
New York City has a population of 8.55 million and 300 square mile area .
Manhattan has 1.64 million and 23 square miles area .
To Find :
How much greater is the population density of Manhattan than New York City.
Solution :
Population density of New York City :
[tex]D_{NY}=\dfrac{8.55}{300}=0.029 \ million/mile^2\\\\D_{M}=\dfrac{1.64}{23}=0.071 \ million/mile^2[/tex]
Now ,
[tex]D_{M}-D_{NY}\\\\(0.071-0.029)=0.042\ million/miles^2[/tex]
Therefore , population density of Manhattan is [tex]0.042\ million/miles^2[/tex] greater than New York City .
Hence , this is the required solution .