The case of Brown, Jones, and Smith is being investigated. One of them committed a crime. During the investigation, each of them made two statements. Brown: “I didn't do it. Jones didn't do it.” Smith: “I didn't do it. Brown did it.” Jones: “Brown didn't do it. Smith did it.” It was later found out that one of them told the truth twice, another lied twice, and the third told the truth once and lied once. Who committed the crime?
Think about whether Jones could have been the thief.

## Solution

The thief is Brown. If we consider the three possibilities - "Brown stole it", "Smith stole it", and "Jones stole it" - we see that only in the case of "the thief is Brown" do the conditions of the problem hold. If the thief is Smith, then both Brown and Jones told the truth. If the thief is Jones, then both Brown and Smith simultaneously told the truth and lied.