单选题 The following data sufficiency problems consist of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements plus your knowledge of mathematics and everyday facts (such as the number of days in July or the meaning of counterclockwise), you must indicate whether
Ａ. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Ｂ. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
Ｃ. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
Ｄ. EACH statement ALONE is sufficient.
Ｅ. Statements (1) and (2) TOGETHER are NOT sufficient.

单选题 In the figure above, is AB＞BC? (Note: Figure not necessarily drawn to scale.)
(1) AB＞CD
(2) (AD-AB)＞(AD-BC)
【正确答案】 B
【答案解析】Statement (1) tells us nothing about the relationship of AB to BC, so the answer cannot be A or D. Statement (2), however, tells us that AB must be a smaller number than BC. This gives us sufficient information to answer the question in the negative, so the answer is B. Note that it does not matter whether the answer to a Data Sufficiency question is yes or no; it only matters that you have sufficient data to answer the question.
单选题 A box contains 90 jelly beans, of which some are orange, some are purple, and some are black. How many black jelly beans are in the box?
(1) There are 27 orange jelly beans.
(2) There are twice as many purple jelly beans as orange jelly beans.
【正确答案】 C
【答案解析】alone is not sufficient, because there could be 6 or 60 black jelly beans in the jar. (2) alone is not sufficient, because there could be 1 orange and 2 purples, or 20 oranges and 40 purples. But (1) and (2) together tell us there are 27 orange jelly beans, 54 purple jelly beans, and therefore 9 black jelly beans.
单选题 Is 3x greater than 100?
(1) 9x=36
(2)
【正确答案】 D
【答案解析】To be able to answer this question, we need to know a numerical value for x, because any numerical value will give a value for 3x that is either greater or less than 100. (1) gives the value of 4 for x, so it is sufficient (3x=81; it is not greater). (2) can be restated as 100＞3x, so 3x cannot be greater than 100, and (2) is sufficient to answer the question.
单选题 How many more dogs than cats are in the veterinarian's office?
(1) There is a total of 30 dogs and cats in the office.
(2) The number of cats is the square root of the number of dogs.
【正确答案】 C
【答案解析】Statement (1) alone is insufficient because it does not give the breakdown between dogs and cats of the 30 animals. Statement (2) alone is insufficient because the pair of numbers described could be 2 and 4, 3 and 9, 4 and 16, and so on. When the two statements are combined, however, there is only one pair of numbers that can match both statements: 5 and 25. That is sufficient information to answer the question.
单选题 If p is a positive integer, and p≠0, is
【正确答案】 A
【答案解析】One way to verify this is to plug in even numbers; the results soon show that the result is always half of p plus 1/2, which is never an integer. You could also simplify the equation to