Fun Riddle: Only People with Very High IQs Can Save These Poor Animals from a Forest Fire
It’s been a while since we’ve challenged our brains, so today, let’s return to a classic river-crossing puzzle with a higher level of difficulty. Here’s the situation for you:
One day, a wildfire breaks out on a distant grassland. It starts small but quickly spreads, burning the entire field. Ultimately, only six creatures survive and are trying to escape the fire: three lions and three antelopes.
While fleeing, they reach a river full of hungry crocodiles waiting below. To escape, they must cross to the left bank of the river. They cannot swim but are lucky to find a raft nearby.
Now let’s assume these creatures have a bit of human intelligence. They can row the raft, but it can only carry a maximum of two animals at a time, regardless of species. At least one animal must stay on the raft to row it across.
Here’s the tricky part: if, at any point, the number of lions is greater than the number of antelopes on either side of the river, the lions will instinctively eat the antelopes. This rule applies even if the raft lands with one lion and one antelope. For example, if a lion and an antelope land on a shore where more lions are present, the antelope will be eaten immediately.
The challenge is to find the fastest way to get all six animals across the river safely without any of them being eaten. Remember, any method that is not the fastest will result in the animals perishing in the fire.
Puzzle Summary
- 6 animals: 3 lions, 3 antelopes, and 1 wooden raft.
- The raft can carry a maximum of 2 animals.
- The number of antelopes must always exceed the number of lions on either side of the river.
- The fastest solution is required, or the animals will die in the fire.
Solution
To solve this puzzle, we need to list all possible decisions for each move and evaluate their outcomes.
Move 1: Take 1 lion and 1 antelope across the river.
- Leave the lion on the far side and have the antelope row back.
Move 2: Bring the antelope back to the starting side.
- Now, 1 lion is on the far side, and all other animals are on the starting side.
Move 3: Take 2 lions across the river.
- Leave 1 lion on the far side and send 1 lion back.
Move 4: Bring 1 lion back to the starting side.
- Now, 2 lions are on the far side, and 1 lion and 3 antelopes are on the starting side.
Move 5: Take 2 antelopes across the river.
- Leave both antelopes on the far side. Now, 2 lions and 2 antelopes are on the far side.
Move 6: Bring 1 lion and 1 antelope back to the starting side.
- Leave the lion on the starting side and take 2 antelopes across the river again.
Move 7: Bring 2 antelopes across the river.
- Now, all 3 antelopes are on the far side, making it safe for the lions to cross one by one.
Final Moves:
- Bring each remaining lion across the river one at a time, ensuring there are always more antelopes than lions on either side of the river.
In total, this solution requires 11 moves, which is the minimum number currently known. Do you have a faster solution? Let us know!