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Let X be random variable which assumes x1x_1, x2x_2, x3x_3, x4x_4 such that 2P(X=x1x_1)= 3P(X=x2x_2)=P(X=x3x_3)=5P(X=x4x_4) , then the probability distribution of X is

Solution

Correct Option: 4

Given that 2P(X=x1)=3P(X=x2)=P(X=x3)=5P(X=x4)2P(X=x_1) = 3P(X=x_2) = P(X=x_3) = 5P(X=x_4)

Let 2P(X=x1)=3P(X=x2)=P(X=x3)=5P(X=x4)=k2P(X=x_1) = 3P(X=x_2) = P(X=x_3) = 5P(X=x_4) = k


Expressing each probability in terms of kk:

P(X=x1)=k2P(X=x_1) = \dfrac{k}{2}

P(X=x2)=k3P(X=x_2) = \dfrac{k}{3}

P(X=x3)=kP(X=x_3) = k

P(X=x4)=k5P(X=x_4) = \dfrac{k}{5}


Since all probabilities must sum to 1:

P(X=x1)+P(X=x2)+P(X=x3)+P(X=x4)=1P(X=x_1) + P(X=x_2) + P(X=x_3) + P(X=x_4) = 1

k2+k3+k+k5=1\dfrac{k}{2} + \dfrac{k}{3} + k + \dfrac{k}{5} = 1


Finding common denominator (LCM of 2, 3, 1, 5 is 30):

15k30+10k30+30k30+6k30=1\dfrac{15k}{30} + \dfrac{10k}{30} + \dfrac{30k}{30} + \dfrac{6k}{30} = 1

15k+10k+30k+6k30=1\dfrac{15k + 10k + 30k + 6k}{30} = 1

61k30=1\dfrac{61k}{30} = 1

k=3061k = \dfrac{30}{61}


Substituting k=3061k = \dfrac{30}{61}:

P(X=x1)=k2=3061×12=1561P(X=x_1) = \dfrac{k}{2} = \dfrac{30}{61} \times \dfrac{1}{2} = \dfrac{15}{61}

P(X=x2)=k3=3061×13=1061P(X=x_2) = \dfrac{k}{3} = \dfrac{30}{61} \times \dfrac{1}{3} = \dfrac{10}{61}

P(X=x3)=k=3061P(X=x_3) = k = \dfrac{30}{61}

P(X=x4)=k5=3061×15=661P(X=x_4) = \dfrac{k}{5} = \dfrac{30}{61} \times \dfrac{1}{5} = \dfrac{6}{61}


The probability distribution of XX is:

XXx1x_1x2x_2x3x_3x4x_4
P(X)P(X)1561\dfrac{15}{61}1061\dfrac{10}{61}3061\dfrac{30}{61}661\dfrac{6}{61}

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