Inverted Cards Puzzle

Problem: One day, Santa and banta were playing cards, but suddenly power went off. Santa randomly inverted position of 15 cards out of 52 cards(and shuffled it) and asked banta to divide the card in two piles with equal number of cards facing up. It was very dark in the room and banta could not see the cards, after thinking a bit banta divided the cards in two piles and quite surprisingly on counting number of  cards facing up in both the piles were equal.

What do you think banta must have done?

Note : Number of cards in each pile need not be equal.

Puzzle Solution:

Just take top 15 cards from the pile and reverse them, now you will have two piles of 15 cards and 37 cards and both of them will have same number of inverted cards.

Inverted cards puzzle explanation:

Lets say there were n inverted cards initially in top 15 cards, obviously in remaining 37 cards number of inverted cards will be 15-n, as total 15 inverted cards.
Now on reversing the 15 cards number of inverted cards would become 15 – n and number of inverted cards will become same in the two piles.

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