I also think it's a fair question, but more about logical reasoning and estimating than basic maths. As an engineer, you could be asked to estimate the number of load balancers needed for X traffic with Y latency - similar problem.
In my experience of those kinds of problems the catch is finding realistic values for X and Y - often nobody is going to hand them to you on a plate and you must work out a way of estimating them - that is the real skill.
