学生通过数学，物理和化学的概率分别为m，p和c。在这些科目中，学生有至少75％的机会通过至少一项，至少50％的机会通过了至少两门，以及40％的机会恰好通过了两门。在m，p和c中绘制以下关系：
1. p + m + c = 27/20
2. p + m + c = 13/20
3. (p) × (m) × (c) = 1/10 (A)只有关系1为真
(B)只有关系2为真
(C)关系2和3是正确的
(D)关系1和3是正确的答案： (D)
解释：
1 - (1 - m) (1 - p) (1 - c) = 0.75 -------(1)
(1 - m)pc + (1 - p)mc + (1 - c)mp + mpc = 0.5 -------(2)
(1 - m)pc + (1 - p)mc + (1 - c)mp = 0.4 -------(3)
From last 2 equations, we can derive mpc = 0.1
After simplifying equation 1, we get.
p + c + m - (mp + mc + pc) + mpc = 0.75
p + c + m - (mp + mc + pc) = 0.65 -------(4)
After simplifying equation 3, we get
pc + mc + mp - 3mpc = 0.4
Putting value of mpc, we get
pc + mc + mp = 0.7
After putting above value in equation 4, we get
p + c + m - 0.7 = 0.65
p + c + m = 1.35 = 27/20 这个问题的测验