How Many Animals Are Going to the River? It's Complicated

Odds are good that you've seen this riddle on social media lately.

One rabbit saw six elephants while going to the river. Every elephant saw two monkeys going towards the river. Every monkey holds one parrot in their hands. How many animals are going towards the river?

You've probably also seen the answer framed as a sort of battle between math and English. One thing's certain—your friends all think they have the answer but no one completely agrees.

The "animals going to the river" riddle from a math perspective

I'll make one thing clear up front and I'll say it in my best Dr. Leonard "Bones" McCoy voice: "Dangit, Jim; I'm an editor, not a mathematician!"

But from a math perspective, the riddle is at least somewhat solvable.

The answer is five.

Did you get the same answer? If you did, you may be in the majority, at least unofficially. My intel shows that five seems to be the most common answer. Let's take a look.

One rabbit saw six elephants while going to the river.

The rabbit is going to the river. Along the way, he saw six elephants.

That means one rabbit is going to the river. So far, so good.

Every elephant saw two monkeys going toward the river.

Things get a bit more complicated here. Did the six elephants each see a different two monkeys? In that case, you'd have 12 monkeys and one rabbit going toward the river—13 animals, total.

But because the sentence doesn't explicitly say that each elephant saw two different monkeys, we use the rules of implicit differentiation and infer that the elephants each saw the same two monkeys.

If you want to know more about explicit and implicit functions in math, Study.com has your back. 

Now, let's return to the critters. We're inferring that each elephant saw the same two monkeys, which means that one rabbit and two monkeys are going toward the river. So far, that's three animals total.

Every monkey holds one parrot in their hands.

Simple. We inferred that two monkeys are going toward the river. Each monkey is holding a parrot, so that's two parrots going toward the river, too.

That gives us:

1 rabbit +
2 monkeys +
2 parrots
...

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