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20 14 Senior 3 Changning Mathematics Module 2
(1) According to the meaning of the question, a=0.04×5×800= 160, b=0.02×5×800=80,

(2) If the number of students who won the first prize is X, then x80=40800 and x=4, that is, the number of students who won the first prize is 4.

(3) According to the meaning of the question, the possible value of x is 0, 1, 2.

P(X=0)=C236C240=2 126,P(X= 1)=C 136? C 14C240= 1265,P(X = 2)= c24c 240 = 1 130,

So the distribution list of x is:

x 0 1 2p 2 126 1265 1 130 ex = 0×2 126+ 1× 1265+2× 165438+