full transcript

From the Ted Talk by James Tanton: Can you solve the computer virus riddle?

Unscramble the Blue Letters


We have four options: turning switch 00 on gives us 11. Turning 01 off tkeas us back to 10, and turning 10 off gives 01. None of those work. tuinnrg switch 11 on gives us 110 by standard binary addition. But we don’t really want three digit numbers. So what if— to keep the result a two digit number— we braek the rules a bit and let this sum equal 22. That’s not a birnay number, but if we regard 2s as the same as 0s, that does indicate the correct disk.

So this suggests a strategy: look at the sum of all the lighted disks we see, regarding 2s as 0s. If it’s already the correct result, flip 00, and if not, find the switch that will make the sum correct.

Open Cloze


We have four options: turning switch 00 on gives us 11. Turning 01 off _____ us back to 10, and turning 10 off gives 01. None of those work. _______ switch 11 on gives us 110 by standard binary addition. But we don’t really want three digit numbers. So what if— to keep the result a two digit number— we _____ the rules a bit and let this sum equal 22. That’s not a ______ number, but if we regard 2s as the same as 0s, that does indicate the correct disk.

So this suggests a strategy: look at the sum of all the lighted disks we see, regarding 2s as 0s. If it’s already the correct result, flip 00, and if not, find the switch that will make the sum correct.

Solution


  1. binary
  2. takes
  3. break
  4. turning

Original Text


We have four options: turning switch 00 on gives us 11. Turning 01 off takes us back to 10, and turning 10 off gives 01. None of those work. Turning switch 11 on gives us 110 by standard binary addition. But we don’t really want three digit numbers. So what if— to keep the result a two digit number— we break the rules a bit and let this sum equal 22. That’s not a binary number, but if we regard 2s as the same as 0s, that does indicate the correct disk.

So this suggests a strategy: look at the sum of all the lighted disks we see, regarding 2s as 0s. If it’s already the correct result, flip 00, and if not, find the switch that will make the sum correct.

Frequently Occurring Word Combinations


ngrams of length 2

collocation frequency
lit disks 3
corrupted disk 3
binary number 2
disk number 2
turning switch 2


Important Words


  1. addition
  2. binary
  3. bit
  4. break
  5. correct
  6. digit
  7. disk
  8. disks
  9. equal
  10. find
  11. flip
  12. lighted
  13. number
  14. numbers
  15. regard
  16. result
  17. rules
  18. standard
  19. suggests
  20. sum
  21. switch
  22. takes
  23. turning
  24. work