other Maths Puzzle Numerical Ability Age Problem

We say that a set of rooks dominate the chessboard if each square is either occupied by a rook, or can be directly attacked by a rook. Obviously the smallest number of rooks which can dominate an 12*12 chessboard is 12, which we can achieve by placing them along the main diagonal.

In 3-dimensional chess, rooks can attack in a straight line in the direction of the coordinate axis. What is the minimum number of rooks which can dominate an 12*12*12 chessboard?

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other Other Question
Your math professor shows you 100 coins placed on his desk with their heads up. He says to you:

"Each time you choose exactly 93 coins and flip them, turning heads to tails or vice versa."

What is the least number of times that you need to do this in order to get all 100 coins tails up? Shakeel wants to spend all his money on sweets. He has enough to buy three small laddus. With the same amount, however, he can buy two large laddus, each of which is 60% larger than a small laddu. What would you advise him to do?