Is this what you expect from expectations? -2

Level 2

The daily problem for Feb 27 asks which of two special dice (1,1,3,3,5,5) and (2,2,2,2,5,5) has a better chance of winning if both dice are rolled simultaneously and the higher roll wins (In case of a tie, you roll both dice again.)

Notice that both dice have the same expected value.

Suppose we have two six-sided dice, A and B, whose faces have integers between 0 and 100 (inclusive).

You are not told what numbers are on the individual faces, but you are told that the probability that A wins is at least 1/2. (And hence the probability that B wins is at most 1/2)

Let E A E_A and E B E_B be the expected values of the rolls of A and B respectively.

Which of the following is true?

E B 50 E A E_B \le 50 E_A E A E B E_A \le E_B E B 100 E A E_B \le 100 E_A but E B > 50 E A E_B > 50 E_A for some dice A and B There is no relation between E A E_A and E B E_B that always holds E A > E B E_A > E_B

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