To find the probability that a Messi fan is also a fan of Ronaldo, we need to find the overlap between the Messi group and the Ronaldo group.
Let's denote the sets as M (Messi), B (Mbappe), D (De Bruyne), and R (Ronaldo). We are given:
1/6 of M are also B (M ∩ B = 1/6 M)
2/5 of B are also D (B ∩ D = 2/5 B)
3/4 of D are also R (D ∩ R = 3/4 D)
We want to find: (M ∩ R) / M
Evaluating Statement (1)
"There is not a single Mbappe fan who is not also a fan of Messi." This means that all Mbappe fans are Messi fans (B is a subset of M). While this tells us the relationship between B and M, it doesn't give us any information about how these fans relate to De Bruyne (D) or Ronaldo (R) in a way that connects back to the whole Messi group. We still don't know if the De Bruyne/Ronaldo fans overlap with the Messi fans outside of the Mbappe group.
Statement (1) is INSUFFICIENT.
Evaluating Statement (2)
"For every Messi fan who is also a fan of Mbappe, there are 5 Messi fans who are also fans of De Bruyne." From the prompt, we know:
Fans of both Messi and Mbappe (M ∩ B) = 1/6 of all Messi fans.
Statement (2) tells us the ratio:
(M ∩ D) = 5 * (M ∩ B)
(M ∩ D) = 5 * (1/6 of Messi fans) = 5/6 of all Messi fans.
Now we look at the De Bruyne/Ronaldo relationship from the prompt:
3/4 of all De Bruyne fans are Ronaldo fans.
The Trap: Statement (2) tells us that 5/6 of Messi fans like De Bruyne. However, we do not know if the "3/4" rule for De Bruyne fans applies specifically to the sub-group of De Bruyne fans who also like Messi. In set theory terms, knowing the overlap of M and D, and knowing the overlap of D and R, does not guarantee we know the overlap of M and R. The Ronaldo fans within the De Bruyne group could be entirely separate from the Messi fans within the De Bruyne group.
Statement (2) is INSUFFICIENT.
Combining (1) and (2)
Even when combined, we have information about how many Messi fans like Mbappe and De Bruyne, and we know all Mbappe fans like Messi. However, we still have no definitive link to Ronaldo other than his relationship with De Bruyne. We cannot assume that the proportion of Ronaldo fans among "Messi + De Bruyne" fans is the same as the proportion of Ronaldo fans among "De Bruyne" fans in general.
Statements (1) and (2) TOGETHER are NOT sufficient.
Correct Answer: E