brandon.boesch
New member
- Joined
- Jul 10, 2011
- Messages
- 2
If the population density of a particular city is given by p(r)= 20/(r+1) in thousands of people per square mile at a distance "r" miles from the center of the city, find the total number of people living within a 10 mile radius of the city center. (Hint: Notice that this is the density per unit area)
I got this problem wrong on my test and i'm not sure why. Here's what I did.
For this problem I tried taking the integral of the function from 0 to 10. This then gave me the population in thousands of people for 10 square mile (result : 20*ln(11) thousand people). With this I drew a box with each side having a length (20*ln(11))^(1/2) Inside this box I inscribed a circle with radius = ((20*ln(11))^(1/2)) / 2
To solve for the population I then used the equation P=(pi)r^2 with r=((20*ln(11))^(1/2)) / 2
Any ideas where I went wrong?
I got this problem wrong on my test and i'm not sure why. Here's what I did.
For this problem I tried taking the integral of the function from 0 to 10. This then gave me the population in thousands of people for 10 square mile (result : 20*ln(11) thousand people). With this I drew a box with each side having a length (20*ln(11))^(1/2) Inside this box I inscribed a circle with radius = ((20*ln(11))^(1/2)) / 2
To solve for the population I then used the equation P=(pi)r^2 with r=((20*ln(11))^(1/2)) / 2
Any ideas where I went wrong?
