Which one of the following statements is/are true?
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Hack:
Because none of the options say that Statement 5 is true, it must be false. This means Statement 3 is true. Among the options, there is only one option that says two correct statements.
Actual solution:
Note that Statement X saying that "Statement Y is false" is equivalent to the known true statement "either Statement X or Statement Y is true, but not both". Thus we know that either Statement 3 or Statement 5 is true, but not both.
Less well-known is that Statement X saying that "Statement Y and Statement Z are both true or both false" is equivalent to the known true statement "an odd number of Statements X, Y, Z are true".
From Statement 2, we can conclude that an odd number of Statements 2, 3, 5 are true. Since Statements 3 and 5 contribute exactly one true statement, Statement 2 must be false.
From Statement 4, we can conclude that "an odd number of Statements 1, 2, 4 are true". Since Statement 2 is false, this becomes "either Statement 1 or Statement 4 is true, but not both".
Thus Statement 2 is false; one of Statements 1, 4 is true; one of Statements 3, 5 is true. This means there are two true statements, so Statement 3 is true and Statement 5 is false.
Now, Statement 1 says that "Statements 2 and 5 have the same truth value". Since Statement 2 and Statement 5 are both false, this means Statement 1 is true. Since only one of Statements 1, 4 is true, we have Statement 4 to be false.
This means Statements 1 and 3 are the only true statements.