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A box contains 90 jelly beans of which some a
问题详情
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.请帮忙给出正确答案和分析，谢谢！
参考答案
正确答案：C
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.
