# Thread: Logic Question

1. ## Logic Question

I need help!!!!

Can someone pls help me with this question

Question: Two of your freinds,Bob and Bill left your calculator in one off their lockers. To test your logic the boys give you chance to ask them one question regarding who's locker the calculator is in. How ever,since they want to test your logic they have decided the one boy will lie to you what ever you ask and other one will tell you the truth what ever you ask. You do not know who will lie and who will tell the truth. You ask Bill ' will Bob tell me it is in his locker?' and Bill says, Yes. You smile in triumph and open the locker containing your calculator. Explain how you knew where calculator was located.

Thanks

2. Hello

Originally Posted by Atrey
I need help!!!!

Can someone pls help me with this question

Question: Two of your freinds,Bob and Bill left your calculator in one off their lockers. To test your logic the boys give you chance to ask them one question regarding who's locker the calculator is in. How ever,since they want to test your logic they have decided the one boy will lie to you what ever you ask and other one will tell you the truth what ever you ask. You do not know who will lie and who will tell the truth. You ask Bill ' will Bob tell me it is in his locker?' and Bill says, Yes. You smile in triumph and open the locker containing your calculator. Explain how you knew where calculator was located.

Thanks
If Bill is the liar, then the statement "Bob will tell me it is in his locker" is false.
Because Bill lies, Bob doesn't lie, which means that what he is going to say will be true.
So Bob won't tell me it is in his locker.

----> the calculator is in Bill's locker.

Now, if Bill doesn't lie, then the statement "Bob will tell me it is in his locker" is true. And because Bill doesn't lie, Bob lies. So what Bob is going to say, "it is in my locker", will be false.

----> the calculator is in Bill's locker.

Do you understand?

3. If the one asked is honest, he will forward the other's lie, thus you will be told a lie.

If the one asked is a liar, he will negate the other's honesty, thus you will be told a lie.

4. ## Thanks

Thanks Guys
I really appreciate that

5. ## Brute force method

You can always just represent the four possibilities. 1. bill has it and lies 2. bill has it and tells the truth 3. bob has it and bill lies 4. bob has it and bill tells the truth. You'll see that, in any case, if bill says "no" bob has it and if bill says "yes" bill has it. This doesn't really give you any insight into the logic but it does clearly display the consequences.