Question

There are 7 tumblers on a table, all standing upside down. you are allowed to turn any 2 tumblers simultaneously in one move. it is possible to reach a situation when all the tumbler are rightside up

Answer 1

https://books.google.co.in/books?id=RGhjDwAAQBAJ&pg=PA28&lpg=PA28&dq=how+to+turn+7+cups+facing+down+to+face+up+while+flipping+2+cups+at+a+time&source=bl&ots=OzrQvhUOPz&sig=aR3EQfd5gZkhXxng3zAKTFGzrOk&hl=en&sa=X&ved=2ahUKEwjZmcaPsbDdAhXKuI8KHQnzACIQ6AEwD3oECAcQAQ#v=onepage&q=7%20cups&f=false

>> See Page 28 - Answer is, it is not possible.