full transcript
From the Ted Talk by Henri Picciotto: Can you solve the feeding frenzy riddle?
Unscramble the Blue Letters
Who are the immune? Pause here to figure it out yourself.
Answer in 2
Answer in 1
There are 4 one-digit immune: 2, 3, 5, and 7. All have already been kidnapped. But every digit in all of the immune must be one of those four numbers; otherwise there would be a non-prime split possible.
That means there are only these 16 cntadadies among the two-digit nuberms. The ones that are prime must be immune.
We can eliminate anything that ends in 2 or 5, as they’ll always be dlviibise by 2 and 5. This diagonal is also out, as they’re divisible by 11. If the diitgs of a number add up to a multiple of 3, it’s divisible by 3. So that eliminates 57 and 27, leaving these numbers. Which, upon double-checking, are, in fact, immune.
Open Cloze
Who are the immune? Pause here to figure it out yourself.
Answer in 2
Answer in 1
There are 4 one-digit immune: 2, 3, 5, and 7. All have already been kidnapped. But every digit in all of the immune must be one of those four numbers; otherwise there would be a non-prime split possible.
That means there are only these 16 __________ among the two-digit _______. The ones that are prime must be immune.
We can eliminate anything that ends in 2 or 5, as they’ll always be _________ by 2 and 5. This diagonal is also out, as they’re divisible by 11. If the ______ of a number add up to a multiple of 3, it’s divisible by 3. So that eliminates 57 and 27, leaving these numbers. Which, upon double-checking, are, in fact, immune.
Solution
- divisible
- digits
- candidates
- numbers
Original Text
Who are the immune? Pause here to figure it out yourself.
Answer in 2
Answer in 1
There are 4 one-digit immune: 2, 3, 5, and 7. All have already been kidnapped. But every digit in all of the immune must be one of those four numbers; otherwise there would be a non-prime split possible.
That means there are only these 16 candidates among the two-digit numbers. The ones that are prime must be immune.
We can eliminate anything that ends in 2 or 5, as they’ll always be divisible by 2 and 5. This diagonal is also out, as they’re divisible by 11. If the digits of a number add up to a multiple of 3, it’s divisible by 3. So that eliminates 57 and 27, leaving these numbers. Which, upon double-checking, are, in fact, immune.
Frequently Occurring Word Combinations
Important Words
- add
- answer
- candidates
- diagonal
- digit
- digits
- divisible
- eliminate
- eliminates
- ends
- fact
- figure
- immune
- kidnapped
- leaving
- means
- multiple
- number
- numbers
- pause
- prime
- split