I solved 67% of the puzzle in 30 seconds but cannot go any further after staring at it for half an hour. I refuse to look up the answer or be told the answer because that's no challenge. I have an open thought on what type of artificial intelligence software might be able to solve this math puzzle. Now, if I can figure out an AI method, that would be a far greater achievement than solving it with my human intelligence (or lack thereof).
The answer is revealed in the following video.
The Number 73
I see 73 is a prime number, therefore, it is not derived from multiplication of other digits in the math puzzle. The number 73 has more of a story behind it than you might imagine. Here is a short-list of some facts about the number 73.
- 73 (seventy-three) is the natural number following 72 and preceding 74. In English, it is the smallest natural number with twelve letters in its spelled out name.
- Seventy-three is the 21st prime number. The 20th prime number is seventy-one. Together, they are the 8th twin primes.
- Reverse the digits in 73 to get 37 which is also a prime number. These are known as permutable primes where any permutation of the digits results in a prime number. For another example, the 3-digit prime number 113 can be permuted to 131 and 311 which are prime numbers.
- 73 is the 21st prime number. 37 is the 12th prime number.
- 73 in binary is 1001001 which is a palindrome (the same forward or backward).
- 73 in Morse Code is a palindrome. 7 is — — · · · and 3 is · · · — — so 73 is — — · · · · · · — — .
- Sheldon in The Big Bang Theory says "73 is the best number".