Real Story of the Cat, the Dog and the Rabbit

Have you seen the email that asks you to figure out the combined weight of a Cat, a Dog and a Rabbit?

This is the kind of email I would normally trash immediately. Math isn’t my strong suit. Oh, I could assign each of the animals  a letter: the Cat a ‘C’, the Dog a ‘D’, and the Rabbit an ‘R’. I could even come up with  three equations: R+C=10; R+D=20; C+D=24. But that would be about as far as I would get before I’d insert a ‘Y’, as in why would I even care.

The Car Guy absolutely loved this email, because his mind likes numbers. He solved the question, even found out what each animal weighed individually, then posted it on Facebook. The response from his friends was almost instantaneous. Some got the answer, some said they were too far into Happy Hour to even guess, and one even posted all the ‘if’, ‘then’, ‘thus’ and ‘therefores’. Even my two young grandsons popped up with the answer, using the ‘guess and check’ (conjecture and proof) method of math that they are learning at school, and it took them less than a minute.

That was when I decided I really did care ‘Y’, and I would find the answer too. First though, I had to fill in the back story so that I could relate to the animals. So here it is:

Grandma had a cat, a dog and a rabbit. They all lived happily on a farm on the right bank of a wide river. The rabbit loved to eat in grandma’s garden, the cat was an excellent mouser, and the dog knew that grandma had a seemingly unlimited supply of kibble and bits.

Somehow (and I’m not too sure how it happened) the three animals woke up one morning on the left bank of the river. This is where the potato farmer lived. The three animals quickly realized that potatoes were not their favourite food, and if they didn’t get back to Grandma’s house quickly, they would perish. The river was too wide to swim, but there was a small boat by the shore and it was just big enough to hold the three of them – as long as they didn’t weigh too much.

The potato farmer had a scale to weigh his bags of potatoes. For some reason the animals couldn’t all get on the scale together, and equally puzzling, they couldn’t get on the scale singly. Instead, they got onto the scale in pairs. With the resulting three pieces of data, they figured out their cumulative weight. They were then able to board the boat, and float across the river without any fear of sinking. The End.

Now you know the real story . Can you answer the question – how much do all three animals weigh? Bonus points if you can tell me how the animals ended up on the left bank of the river AND ‘Y’ they had to weigh themselves in pairs.

I’ll post some answers in the comment section. Don’t peek! I’ll give you a hint though. There is more than one way to find the answer!