Official Solution: A tea shop placed 27 sealed jars of loose leaf tea on two shelves. On each shelf, the jars are arranged from lightest to heaviest. If the heaviest jar on the lower shelf weighs 1.18 kg, and the lightest jar on the upper shelf weighs 1.32 kg, what is the median weight of the 27 jars? First, since 27 is odd, the median is the 14th jar when all 27 jar weights are listed from lightest to heaviest.
Next, since on each shelf the jars are arranged from lightest to heaviest, and the
heaviest lower shelf jar is 1.18 kg while the
lightest upper shelf jar is 1.32 kg, every jar on the lower shelf is lighter than every jar on the upper shelf.
(1) The average arithmetic mean weight of the 27 jars is 1.25 kg.
Knowing the mean is 1.25 kg does not tell us what the 14th jar weighs. Not sufficient.
(2) The lower shelf holds one more jar than the upper shelf.
This implies that the lower shelf holds 14 jars and the upper shelf holds 13 jars. Since every lower shelf jar is lighter than every upper shelf jar, and the
heaviest lower shelf jar weighs 1.18 kg, that jar must be the 14th jar overall in the lightest to heaviest ordering. So, the median weight of the 27 jars is 1.18 kg. Sufficient.
Answer: B