91 and River crossings

The age-old river crossing puzzle is humorously presented and beautifully illustrated with manipulatives that can easily be printed, cutout, and assembled. It will be a winner with children and adults alike.

The puzzle is this: The farmer needs to get a bag of corn, a chicken, and a fox across a river. The boat is small and can only hold the farmer and one other thing at a time. The farmer cannot ever leave the chicken with either the corn or the fox because one of them will be eaten before he returns. He can take several trips across the river, but how does he get all three across?

Pat’s Blog gives a history of the famous puzzle and its variations, and TV Tropes gives the solution to the puzzle here.

91 is a composite number. 91 = 1 x 91 or 7 x 13. Factors of 91: 1, 7, 13, 91. Prime factorization: 91 = 7 x 13.

91 is never a clue in the FIND THE FACTORS puzzles.

91 is prominent in this cool pattern: