一道英文数学概率题A box contains 4 black cubes and 6 white cubes.A cube is drawn from the box.Its colour noted and a cube of the other colour is then added to the box.A second cube is then drawn.(a).If both cu
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(a) 5/7
(b) 9/13
======以下答案可供参考======
供参考答案1:
(a).5/7
(b).5/7
供参考答案2:
a.6/10*5/10=1/4
b.6/10*6/11+4/10*4/11=16/110+36/110=26/55