GMAT
题目
Into empty Jar X, Jen places two black marbles and three white marbles.
Into empty Jar Y, she places five black marbles and four white marbles.
She then draws one marble at random from each jar.
Quantity A
The probability that both marbles drawn are black
Quantity B
The probability that both marbles drawn are white
解析
数值A
P（两颗弹珠均为黑色）= P（从罐子X取出黑色弹珠 **且** 从罐子Y取出黑色弹珠）
= P（从罐子X取出黑色弹珠）× P（从罐子Y取出黑色弹珠）
= 2/5 × 5/9
= 2/9
数值B
P（两颗弹珠均为白色）= P（从罐子X取出白色弹珠 **且** 从罐子Y取出白色弹珠）
= P（从罐子X取出白色弹珠）× P（从罐子Y取出白色弹珠）
= 3/5 × 4/9
= 12/45
= 4/15
由于 4/15 > 2/9，正确答案为B
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