What types of problem developed due to the rapid growth of urban areas

More people = less stuff for each person. If a place grows super fast, poverty is going to be everywhere. Also, worse conditions for the people.

Increase in population leads to many issues. First, the more people who inhabit an area, the more resources are needed. In time, eventually the resources will run out because they are being used quicker than they are being replaced.
Second, there will be more pollution. Humans use a lot of fossil fuel and other harmful chemicals that ruin the environment. Urban areas are known to have horrible air pollution.
Third, there will be less areas for people to live, therefore the city will have to expand. City expansion leads to deforestation, more pollution, destruction of habitats for wild animals, and endless horrors.

In short, population needs to be controlled, or humans must develop cleaner ways of living. Hope this helped.