For this case we have the following conversion factor:
[tex] 1 mi ^ 2 = 640 acres [/tex]
The population density is given by:
[tex] D = \frac{x}{y} [/tex]
Where,
x: total number of people
y: total area
Substituting values we have:
[tex] D =\frac{750000}{49 * 640} [/tex]
[tex] D = 23.9 \frac{people}{acre} [/tex]
Rounding the nearest whole we have:
[tex] D = 24 \frac{people}{acre} [/tex]
Answer:
The population density in San Francisco is:
[tex] D = 24 \frac{people}{acre} [/tex]