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 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.
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.
参考答案：C
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.