Abigail, Bridget and Claudia often eat dinner out.
- Each orders either coffee or tea after dinner.
- If Abigail orders coffee, then Bridget orders the drink that Claudia orders.
- If Bridget orders coffee, then Abigail orders the drink that Claudia doesn’t order.
- If Claudia orders tea, then Abigail orders the drink that Bridget orders.
Who always orders the same drink after dinner?
Answer
From (1) and (2), there are 6 possibilities.
| Possibility | Abigail | Bridget | Claudia |
|---|---|---|---|
| P1 | coffee | coffee | coffee |
| P2 | coffee | tea | tea |
| P3 | tea | coffee | coffee |
| P4 | tea | tea | tea |
| P5 | tea | coffee | tea |
| P6 | tea | tea | coffee |
Then, from (3), P1 and P5 are eliminated. And from (4), P2 and P5 are eliminated.
So based on the remaining possibilities P3, P4 and P6, we know that Abigail always orders the same drink (tea) after dinner.