14/09/2022

In a column in Folha, Viana proposes a mathematical challenge.

Foto: Pexels

Reproduction of Marcelo Viana's column in Folha de S. Paulo.

1. Lost in a dark labyrinth, Malu comes across three imposing stone doors. Engraved on the left door is "The exit is here." On the middle door, "The exit is through one of these doors." On the right door, "The exit is through the middle door." A deep voice echoes in the labyrinth: "Only one of the doors tells the truth. You will have only one chance: if you fail, you will remain here for all eternity…" What should the unfortunate Malu do?

2. Abel is traveling with a dog, two chickens, and a bag of poultry feed. Upon reaching a river, he discovers that the only way to cross is by using a rowboat with three seats. He and the animals each occupy one seat, but the bag is large and takes up two seats.

Abel, the only one who rows, could make several trips to take everyone. But if he leaves any of the chickens unsupervised with the bag, she will eat the feed. The dog is also hungry and, if left alone with any of the chickens, he will eat her. But the dog is also timid: if left alone with the two chickens, he will run away and never come back.

How can Abel safely transport everyone to the other side?

3. Marcos always picks up his daughter Ana from school at 5 PM. Methodical, he drives at a constant speed. But today Ana wasn't feeling well, so she left earlier and walked home. She had been walking for an hour when her father met her on the road. They turned around and arrived home 40 minutes earlier than usual. How much school time did Ana miss?

4. John and Mary love having fun with math. This time, Mary came up with the following game. Consider a two-digit number, for example, 45. Square each digit and add the results: in this case, it gives ^4² + ^5² , which is 41. Then, repeat this operation with the result obtained, successively: ^4² + ^1² = 17, then ^1² + ^7² = 50, etc.

To read the full text, visit the newspaper's website.