Three coins are pointing up, and 2 coins are flipped each time. Is it possible to make all three coins face down? The solution is to calculate the parity, and flip each coin if it is flipped odd times

Three coins are pointing up, and 2 coins are flipped each time. Is it possible to make all three coins face down? The solution is to calculate the parity, and flip each coin if it is flipped odd times; all coins

Use 0 and 1 to represent the two sides of the coin. It used to be 0, 0, 0 (the sum is 0, an even number), but it needs to be changed to 1, 1, 1 (the sum is 3, an odd number)

Because 2 coins need to be converted at a time, the changed value of three coins can only be 2 (two 0s become 1), 0 (one 1 becomes 0, one 0 becomes 1), or - 2 (two 1s become 0), which means the changed value is an even number.

Obviously, 0 cannot be obtained by adding and subtracting n even numbers to 3.

So it proved successful.