Today, my friend Gasan showed me this. I was totally stunned. The question is “What are the top cities by population in the world?”. Not the population of the metro area but just the city proper. (The metro area list is very different) . You have to do this without Googling. I will give you the city names. Can you rank them?
Try it and then check in Google. Or I will post the answers:

Beijing, Delhi, Guangzhou, Istanbul, Karachi, Moscow, Mumbai, Sao Paulo, Shanghai, Tianjin (in China)

Note that the top 4 cities by metro area population – Tokyo, Seoul, Mexico City and New York City do not figure in the above list!!!