Rational or Irrational Numbers

How does the title of the example "Using Irrational Numbers" jibe with the question "To the nearest ten meters, how much farther is ..."?

I get that this is a pre-algebra textbook, but it seems to me that a discussion of irrational numbers should deal with irrational numbers, or at least with answers rounded to the nearest hundredth or something. 

Maybe the start of a discussion of significant figures and tolerance and error?