Question

There are 20 coins placed on a table such that tails is showing up. The electricity suddenly goes off and a boy sitting nearby inverts a few coins and then asks another boy to select some coins such that number of inverted coins is equal in every other subpart. The other boy selects 8 coins and inverts those 8 coins. When the electricity comes back, he sees an equal number of inverted coins in both subparts. How many coins did the first boy invert?

Answer 1

At first the boy inverted 2 coins to heads.So when the other boy inverted the other 8 coins then the the number of heads was equal to numbers of tails i.e 10/10 each.