Are all the ants as heavy as all the humans?

Question

During my viva voce examination of maths especially subjects related to differential equations and mathematical biology, one of the professor asked me the following question:

Are all the ants as heavy as all the humans?

I thought as the human population will be very less as compared to the ant population, we can assume both of them having the same weight. But the professor said, ants population will be more. After the exam I read an article regarding this, but I don't know during a viva exam of courses like differential equations and mathematical biology, how one should try to answer this question.

Answer 1

This Wikipedia article says that the total biomass of ants and humans may be more or less equal, although there is considerable uncertainty over the ant biomass. The population of ants is much greater than the human population, but each individual ant obviously has a much smaller mass, by a factor of more than $10$ million.

The purpose of asking this type of question in an examination is to get you to explain your reasoning process when approaching the problem. You are not expected to know the answer - indeed, in this case it seems that no-one knows the actual answer.

Answer 2

I would characterize this as a Fermi problem type question. If such a question comes up in an exam, I would not think that giving the right answer will get you points, but rather you should give a good argument. So: What are your assumptions and how do they synthesize to your conclusion. In the end, you are not tested on Biology, so no one could blame you if you vastly over or underestimate the number of weight of ants. But, you should be able to explain your thought process.