Solution: The Three by Four Flip
The Three by Four Flip challenged students to lay four cards face down and get all of them facing up by turning over three cards at a time. The challenge was to do this in the fewest possible number of moves. Our thanks to Mrs. Meaders from Christopher School in Chicago, Illinois, who sent us samples of her students’ work. The four-step solution given below was discovered by Joshua Cruz, Claudia Cruz, Antonio Estrada, Ryan Greene, and Serina Moncada.
Move one: Flip cards 1, 3, 4
Move two: Flip cards 1, 2, 3
Move three: Flip cards 2, 3, 4
Move four: Flip cards 1, 2, 4
There are many other possible solutions to this problem, but each one will follow the pattern described in the following table.
