Official Guide Problem Solving 129

praneeth wrote:I think this is one of the questions that the OG has a wrong answer. The answer explanation goes on to say that the range of values for miles is 284 to 295 which makes no sense since correct range should be 285 to 294 for it to round to 290.

That's how it gets to the answer.

Same issue with the gallon count.

The explanation in the OG is not good, but the answer is certainly correct, for the reasons permafrost gave above. While we can actually be certain that the miles per gallon was between

285/12.5 and 295/11.5

since that's the case, we can be absolutely certain that the miles per gallon was between

284/12.5 and 295/11.4

because 284/12.5 is less than 285/12.5, and 295/11.4 is greater than 295/11.5. The question does *not* ask, "what range of values gives the *only* possible values for Cindy's miles per gallon?". Instead it asks "The number of miles per gallon must have been between..." If there had been an answer choice which said "0.1 and 1000", it would be correct, because we can be completely sure that Cindy's miles per gallon was larger than 0.1 and less than 1000. In the same way, answer D is correct here, even if the range includes some values that could not possibly be equal Cindy's mileage per gallon.