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GATE 2021 ST – Question 32

Probability · Moments and Inequalities · 1 mark · Numerical answer

X has density (3/13)(1−x)(9−x) on 0<x<1,zero otherwise. Find (4/3)E[X(X²−15X+27)],to two decimals.

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Correct answer: 8.60 to 8.75

Explanation

Multiply the polynomial by the density. The expectation times 4/3 is (4/13)∫₀¹[x⁵−25x⁴+186x³−405x²+243x]dx. Integrating termwise gives (4/13)[1/6−5+186/4−135+243/2]=26/3≈**8.67**.

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