Question

Zhang Tao has many guests in his home. He decides to measure the population density in his home. What would be an appropriate unit for Zhang Tao’s purpose?

Answer 1

Density is the amount of something per unit area.

For population density, consider:

$\frac{guests}{ {m}^{2} } \: or \: \frac{guests}{room} \:$

Answer 2

Good question. Let's try this. How about People per meter squared. The average 2 bedroom apartment in the city near where I live is about 94 square meters.  If there were say 100 people at a party in his home, then the number of people per square meter would be 100 / 94 = 1.06 people / square meter.

If however he called those in his home to join him for breakfast and 7 people responded then he would have 7 / 94 = 0.0745 people per m^2 When the number is this small, it might make sense to go the other way. (m^2 per person). 94/7 = 13.4 meters per person. That makes far  more sense. It means that every person has 13.4 meters^2 that he could call his own.