I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "According to the Sixth China Census, the total population of the City of Nanjing reached 8.005 million in 2010. The statistics in 2011 estimated the total population to be 8.11 million. The birth rate was 8.86 percent and the death rate was 6.88 percent. The urban area had a population of 6.47 million people. The sex ratio of the city population was 107.31 males to 100 females."?
A:
where was the ratio of 107.31 males to 100 females?