The missing number is 1,620. The digits in the tens places (green in the figure below) of the numbers in columns 1, 2, 4 and 5 are added together. The total value is represented by the digits in ...

A picture circulating online challenged people to determine the missing number from what looked like a simple sequence of numbers from 1 to 19. "Which number is missing?" the puzzle asks.

Here's the puzzle: Can you find the missing number? Courtesy of Puzzles9 If you're stumped, don't worry. Here's how to fill in that last number. From left to right, let's label the pentagons A, B ...