A random variable \(X\) has \(P(X=x)=kx\) for \(x=1,2,3,4\). Then \(E(X)\) is
A. 2
B. 3.5
C. 3
D. 2.5
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Best answer
Answer: C. 3
\(k(1+2+3+4)=1\Rightarrow k=\frac1{10}\); \(E(X)=\frac{1+4+9+16}{10}=3\).
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· 23 Oct 2026
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