Bunuel
Each dinner at Restaurant X includes a pair of side dishes, which a customer chooses by selecting any one side dish from list A and any one side dish from list B. There are a total of 18 possible pairs of side dishes, and no side dish appears on both lists. If there are fewer side dishes on list A than on list B, how many side dishes are on list B ?
(1) There are a total of 9 side dishes on the two lists.
(2) There are a total of 3 side dishes on list A.
Since there is no overlap between the two lists, and since we need to select one item from each of the two lists to make a pair of side dishes, we have:
number of pairs = number of items on list A × number of items on list B = a × b
We know that ab = 18 and a < b and need to answer the question:
b = ?
Statement One Alone:=> There are a total of 9 side dishes on the two lists.
a + b = 9
From the question stem we know that a and b are integers greater than 1 [because there must be more than 1 item on a list so that a customer has a choice], ab = 18, and a < b, so we have only two cases to evaluate:
If a = 2 and b = 9, then a + b ≠ 9, so this is an invalid case.
If a = 3 and b = 6, then a + b = 9, so this is the only valid case, and thus there are 6 side dishes on list B.
Statement one is sufficient. Eliminate answer choices B, C, and E.
Statement Two Alone:=> There are a total of 3 side dishes on list A.
a = 3
From the question stem, we know that we have only two cases to evaluate:
If a = 2 and b = 9, then a ≠ 3, so this is an invalid case.
If a = 3 and b = 6, then a = 3, so this is the only valid case, and thus there are 6 side dishes on list B.
Statement two is sufficient.
Answer: D