Question 55
Two fair dices with faces numbered 1 to 6 are thrown and their points are added. The thrower is given Rs. 40 for a score of 12 and he has to pay Rs. 2 if the score is less than 12. What is his expectation about gain or loss per throw?
Solution
Probability of getting 12(6,6) = $$\frac{1}{6}\cdot\frac{1}{6}=\frac{1}{36}$$
Gain or loss per throw = 40($$\frac{1}{36}$$) + (-2)($$\frac{35}{36}$$) = $$\frac{40}{36}-\frac{70}{36}=-\frac{30}{36}=-\frac{5}{6}$$
Loss of Rs $$\frac{5}{6}$$ for one throw.
Answer is option D.
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