A similar question: approximately how many IPv4 addresses are there?
See also: "Latency Numbers Every Programmer Should Know"
The rest is fluff and hidden cultural test: "Do you have the same history as I do?"
TBH, I'm slightly disturbed by these "young people" who have completely no idea how machines actually work.
But the question is silly because there are better ways to ask people if they know in case you require that they know and you probably shouldn't be asking anything at all if you don't care if they know.
I agree with you here, but I would like to think if I were interviewing someone and they told me such, I would then ask something like "How would you go about finding this information out?", and continue down that line (I wouldn't just accept "I'd google it", I'd want something more in depth, even though that would technically be correct).
Personally, the question reads like "have you ever pieced-together a computer?" and one could argue that the question could weed out better candidates for certain positions. A growing number of younger engineers have only used machines that come glued-together, and never had to compare performance vs. price as they chose a CPU.`
But this kind of thing may only be mentioned in one sentence in an intro computer systems course, and most young people wouldn't care about how many operations a CPU can do.