Frank is on his way to the Wonder Land. He loses his way and
reaches a junction of three streets: Gold Street, Park street and
High Street. There is a guardian on each street. Frank asks each of
them for direction. The Gold Street guardian answers: “The Gold
Street does not lead you to the Wonder Land.” The Park Street
guardian answers: “The Park Street does not lead you to the Wonder
Land.” The High Street guardian answers: “The Park Street leads you
to the Wonder Land.” Frank knows the following facts: “Only one of
the three streets leads to the Wonder Land, the other two do not.”
“Exactly one of the three answers is true.” Use
propositional logic to prove that the Gold street
leads to the Wonder Land but no the Park Street nor the High
Street.