Can You Solve The Fish Riddle? By Steve Wyborney (Transcript)

TED-Ed Lesson TRANSCRIPT

You are the cargo director on the maiden voyage of the S.S. Buoyant. And you’ve agreed to transport several tanks containing the last specimens of a critically endangered fish species to their new aquarium.

Unfortunately, as you’re passing through shark-infested waters, the boat is battered by a fierce storm, throwing your precious cargo overboard.

And to make matters worse, no one seems certain just how many fish tanks are missing.

Fortunately, you have a rescue sub at your disposal, but only enough fuel for one trip to the ocean floor. You need to know where the tanks are so you can gather them all in one quick pass. Not a single fish can be lost.

You decide to scan the three sectors of the ocean floor where the cargo could have landed. Thermal imaging shows 50 organisms in the area, and you quickly realize that that number includes both your fish and some ravenous sharks.

You flip on the sonar to get a better look. The image for Sector Alpha shows four tanks and two sharks, the image for Sector Beta shows two tanks and four sharks, and the image for Sector Gamma is blank.

Your sonar has malfunctioned, and you’re going to have to go with the info you have. You check the shipping notes, but all you learn is that each tank had the same number of fish inside.

The cargo hold had space for anywhere from 1 to 13 total tanks.

And finally, the old captain tells you that this area has the odd property that no two sectors can have the same number of sharks, but every sector will have at least one, and no more than seven.

There’s no time to waste. The tanks won’t withstand the pressure much longer.

As you descend in the sub, you review everything you know. How many fish tanks do you need to find in Sector Gamma? Hurry, the fate of an entire species depends on you.