Assuming the jug that the wizard drank from that morning (right after waking) had water that only came from one well, which number well did that water come from?

Steps to Solve

1. Identify the Wells and Their Risks

There are 7 wells on the island, labeled Wells 1 to 7.

• Well 1 is safe to drink from.
• Wells 2, 3, 4, 5, and 6 are poisoned.
• Well 7 is also poisoned.

2. Understanding the Wizard's Situation

The wizard drank water right after waking up and filled up his jug from one of the wells. He realizes that his house's windows were broken, indicating someone might have tampered with his jug.

3. Determine How Poison Affects People

According to the rules:

• Drinking from a poisoned well (2-6 or 7) results in illness after 5 hours.
• If a person drinks from three poisoned wells within 24 hours, they become immune to the effects of the poison for future encounters within that timeframe.

4. Analyze What the Wizard Experienced

Since he drank right after waking up:

• If he only drank from a single poisoned well, he would feel the effects after 5 hours, meaning he wouldn't have acted normally.
• Since it’s indicated later that he had pure water, it implies that he must have only filled his jug from the one safe well.

5. Conclusion for the Safe Well

Since Wells 2 to 7 are poisonous, and Well 1 is safe, the wizard must have drunk from:

• Well 1 (the only non-poisoned well)