GMAT一道数学题(datasufficiency)求解
IsthemeasureofoneoftheinteriorofquadrilateralABCDeaqualto60degrees?
(1)Twooftheinteriorangelsarerightangels.
(2)ThedegreemeasureofangelABCistwicethedegreemeasureofangelBCD.
为什么不选B呢,难道条件(2)不能单独推论出该平行四边形有一个角必为60°吗:两个内角和应为180°,角ABC=2角BCD,那不就是得出角ABC为120°,而角BCD为60°吗?