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Let X be a random variable. Let E (X) and Var (X) denote the mean and the variance of X respectively. Then match List-I with List-II

List-IList-II
(A) If Var (X) = aa, then Var (2X + 3) is(I) 11aa
(B) If E (X) = aa, then E (2X) is(II) 6aa
(C) If Var (X) = aa, then Var(3X - aa) + Var (2x+β\sqrt{2}x + \beta) is(III) 4aa
(D) If E (X) = 5a12\frac{5a}{12}, then E (12X + aa) is(IV) 2aa

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 3

For Expectation: E(aX + b) = a·E(X) + b

For Variance: Var(aX + b) = a²·Var(X), where constants vanish in variance calculations.


(A) If Var(X) = aa, then Var(2X + 3) is

The coefficient of X is 2.

Var(2X + 3) = (2)2⋅Var(X)(2)^2 \cdot \text{Var}(X)

=4×a= 4 \times a

=4a= 4a

Match: (A) → (III)


(B) If E(X) = aa, then E(2X) is

E(2X) = 2⋅E(X)2 \cdot E(X)

=2×a= 2 \times a

=2a= 2a

Match: (B) → (IV)


(C) If Var(X) = aa, then Var(3X - aa) + Var(2X+β\sqrt{2}X + \beta) is

The constant −a-a vanishes in variance:

Var(3X - aa) = (3)2⋅Var(X)(3)^2 \cdot \text{Var}(X)

=9a= 9a

The constant +β+\beta vanishes in variance:

Var(2X+β\sqrt{2}X + \beta) = (2)2⋅Var(X)(\sqrt{2})^2 \cdot \text{Var}(X)

=2a= 2a

Total = 9a+2a9a + 2a

=11a= 11a

Match: (C) → (I)


(D) If E(X) = 5a12\frac{5a}{12}, then E(12X + aa) is

E(12X + aa) = 12⋅E(X)+a12 \cdot E(X) + a

=12×5a12+a= 12 \times \frac{5a}{12} + a

=5a+a= 5a + a

=6a= 6a

Match: (D) → (II)


Therefore, the correct matching is:

(A) - (III), (B) - (IV), (C) - (I), (D) - (II)

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