New colleague Paul Schneider repeated this example in brown bag seminar on teaching:†
Honestly, I wonder how many adults would respond that this question is not answerable.
In doing quantitative work, particularly with undergraduates, I run into something like this. It’s a sure fire sign that a student doesn’t understand the problem their working with if they print out every possible digit produced by their computer or calculator. Rounding, I guess, is an indicator of comfort with your level of understanding.
† I believe the cite for this is Bransford, John D., and Barry S. Stein. "The IDEAL problem solver." (1993).