Question 74
Mieke has a stack of $21$ cards. Mieke repeats the following operation:
She takes the top two cards from the stack, changes their order, and then puts them at the bottom of the stack (so the top card becomes the bottom card).
Mieke repeats this operation until the cards are back in their original order.
How many times does Mieke perform the operation?
She takes the top two cards from the stack, changes their order, and then puts them at the bottom of the stack (so the top card becomes the bottom card).
Mieke repeats this operation until the cards are back in their original order.
How many times does Mieke perform the operation?