Over the years the city has been home to people of various ethnicities, resulting in a range of different traditions and cultural practices. In one decade, the population increased from 427,045 in 1991 to 671,805 in 2001. The population was projected to reach 915,071 in 2011 and 1,319,597 by 2021. To keep up this population growth, the KMC-controlled area of 5,076.6 hectares (12,545 acres) has expanded to 8,214 hectares (20,300 acres) in 2001. With this new area, the population density which was 85 in 1991 is still 85 in 2001; it is likely to jump to 111 in 2011 and 161 in 2021.

Answer this question, if possible (if impossible, reply "unanswerable"): How dense was the population of Kathmandu in 1991?
85