Blue Door & Red Door

One teacher always tells the truth. The other always says the opposite.

Archie and Oliver find a Blue door and a Red door. Behind one is a prize; behind the other is nothing.

Archie asks Ms. Linfield: “Would Mrs Rea say the Blue door is the correct one?”

Ms. Linfield answers: “Yes.”

1. If Ms. Linfield tells the truth (Mrs Rea says the opposite), is Blue correct?
2. If Mrs Rea tells the truth (Ms. Linfield says the opposite), is Blue correct?
3. Which door should they choose?
4. Why is asking about the other teacher's answer tricky?

Work-it-out table

	IF Ms. Linfield tells the truth	IF Mrs Rea tells the truth
Who must say the opposite?
Would Mrs Rea say Blue is correct?
Ms. Linfield said “Yes”. True or opposite?
So is the Blue door correct?
Final door

Grown-up answer key

1 & 2: In both cases, Blue is not the prize door.

3: Choose the Red door.

4: The answer already includes the other person's truth/lie twist, so it needs careful unpicking.

Table: Opposite person is Mrs Rea / Ms. Linfield. Rea would say Blue (case 1) / would not (case 2). Linfield's “Yes” is true / opposite. Blue correct? No / No. Final: Red.