Get smart curated videos delivered to your inbox.   SUBSCRIBE
The Kid Should See This

Can you solve the risky disk riddle?

Watch more with these video collections:

Malicious code has hijacked your mainframe, but luckily you’ve seen this before: The malicious code specifically “corrupts one of the 4 disks that run your mainframe, represented by lights showing which are on and which off.”

If your antivirus squad can destroy the corrupted disk, the malicious code will be defeated, but if you choose wrong, the entire system will be wiped out. How can you tell which of the four disks has been corrupted? Can you solve the risky disk riddle?

This TED-Ed lesson by mathematician James Tanton, with animation by Igor Coric of Artrake Studio, shares the thinking behind solving this challenge. Pause the video at 1m20s if you want to figure it out on your own.

which one is corrupted?
From TED-Ed’s Dig Deeper lesson notes:

“The solutions to these puzzles make use of the binary representation of numbers. For a fun, straightforward, and visual way to understand the binary number system have a look at the opening explorations of the Exploding Dots story from the Global Math Project. (Millions of students and teachers have!)

“Solving the puzzle for a count of discs a large power of two relies on counting the 1s that appear in the binary representations of numbers and keeping track on whether these counts are even or odd. Mathematicians use the term parity to describe the idea that an object in a certain scenario might be in one of two states: up or down, black or white, or, in the case of the counting numbers, even or odd, for instance.”

How does binary code work? Watch that video next. Then check out this Binary Marble Adding Machine.

Then try these TED-Ed riddles next:
Can you solve the sorting hat riddle?
• Can you solve the troll’s paradox riddle?
• The Sea Monster Riddle
• Can you solve the honeybee riddle?
• Can you solve the temple riddle?

This Webby award-winning video collection exists to help teachers, librarians, and families spark kid wonder and curiosity. TKSST features smarter, more meaningful content than what's usually served up by YouTube's algorithms, and amplifies the creators who make that content.

Curated, kid-friendly, independently-published. Support this mission by becoming a sustaining member today.

🌈 Watch these videos next...

Will YouTube Ever Run Out Of Video IDs?

Rion Nakaya

What’s the fastest way to alphabetize your bookshelf?

Rion Nakaya

What’s going on inside your computer?

Rion Nakaya

Turing Tumble, a DIY mechanical computer powered by marbles

Rion Nakaya

The Universal Tea Machine, a huge mechanical ‘adding computer’

Rion Nakaya

The Sea Monster Riddle

Rion Nakaya

The Fire Crystal Riddle and proof by contradiction

Rion Nakaya

The ancient secrets revealed by deciphered cuneiform clay tablets

Rion Nakaya

Noor Inayat Khan: From Pacifist to Spy

Rion Nakaya