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Random Variables, Expectation & Variance · Question 43 of 68

Question 43

MediumOriginal question

A die is thrown. You win as many rupees as the number on the die if it is even, and lose ₹2 if it is odd. What is your expected gain per throw?

Options for question 43

Show the answer and explanation
CorrectNot quiteAnswer A

Correct answer: A

Explanation

  1. Gains: ₹2, ₹4, ₹6 each with probability 16\frac{1}{6}, and −2-2 with probability 12\frac{1}{2}.

  2. E=2+4+66−2×12=2−1=1E = \frac{2 + 4 + 6}{6} - 2 \times \frac{1}{2} = 2 - 1 = 1 rupee.

Worth noting

₹2 counts the winnings but not the expected loss on odd numbers.

Concept
The expected gain in a game
Typical time
90 s
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The rule this testsMathematical expectation
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Ten questions from Random Variables, Expectation & Variance, at your own pace.

Practise this chapter →

Ten questions from Random Variables, Expectation & Variance, at your own pace.