Each approximate result has its decimal digits go on forever without any pattern. So we cannot write those values as a fraction of two integers. The decimal expansion must have some kind of pattern that repeats forever, so we could consider it rational.
Only choice B results in a whole number. The value 14 is the same as 14/1, showing it can be written as a fraction of two integers. Therefore choice B is rational.
Write the equation out: (total cost: 0.35C[per carton] + 75[delivery charge]) ≤ 500. Subtract 75 on both sides and it would be: 0.35C ≤ 425. Divide 0.35 on both sides and you'll get C ≤ 1214. Therefore, the maximum # of cartons that Elvira can buy is 1214 cartons of milk.
