BRAIN TRIVIA
Logic Puzzle: Three kids (Alex, Billy, and Casey) were in the kitchen when a cookie went missing.
Alex says: “I didn’t take the cookie.”
Billy says: “Casey took the cookie.”
Casey says: “Billy is lying.”
Only one is telling the truth. Who took the cookie? 🍪
Hint:
Go through each of the kids, one at a time, and assume they’re telling the truth. Since only one of the kids’ statements can be true, see whose statement makes the other two false.
Solution:
Alex says: “I didn’t take the cookie.”
Billy says: “Casey took the cookie.”
Casey says: “Billy is lying.”
Remember: only one is telling the truth. The other two are lying.
If Alex is telling the truth, he didn’t take the cookie. That means either Billy or Casey took it. Since only one person can be telling the truth, Billy must be lying. But Casey says Billy is lying, which would make Casey’s statement true. That means Alex and Casey are both telling the truth. So, Alex cannot be telling the truth.
If Billy is telling the truth, Casey took the cookie. But if Casey took it, then Alex’s statement (“I didn’t take the cookie”) is also true. That would make both statements true. So, Billy cannot be telling the truth.
If Casey is telling the truth, Billy is lying. That means Billy’s statement (“Casey took the cookie”) is false, so Casey did not take the cookie. Since Casey didn’t take it and Alex says he didn’t take it (but Alex must be lying), that means Alex took the cookie. ✅