CAT 1991 — QA Question 27
Rolling DiceEasy
A player rolls a die and receives the same number of rupees as the number of dots on the face that turns up. What should the player pay for each roll if he wants to make a profit of one rupee per throw of the die in the long run?
Answer & solution
Correct answer: Rs. 2.50
Rs. 2.50
- B
Rs. 2
- C
Rs. 3.50
- D
Rs. 4
Solution
Since in the long run the probability of each number appearing is the same, we can say in ‘n’ throws one can get 1, 2, 3, 4, 5 and 6, n/6 times each.
Hence he would earn (1 + 2 + 3 + 4 + 5 + 6)n/6 = Rs. 7n/2 = Rs. 3.5n.
∴ His average earning for each through is 3.5n/n = Rs. 3.5
In order to make a profit of 1 Re. per throw his cost for the each through should be = 3.5 – 1 = Rs. 2.50
Hence, option (a).