Best riddles for teens

simplecleanlogicinterview

You are blindfolded and 10 coins are place in front of you on table. You are allowed to touch the coins, but can't tell which way up they are by feel. You are told that there are 5 coins head up, and 5 coins tails up but not which ones are which. How do you make two piles of coins each with the same number of heads up? You can flip the coins any number of times.
Make 2 piles with equal number of coins. Now, flip all the coins in one of the pile. How this will work? lets take an example. So initially there are 5 heads, so suppose you divide it in 2 piles. Case: P1 : H H T T T P2 : H H H T T Now when P1 will be flipped P1 : T T H H H P1(Heads) = P2(Heads) Another case: P1 : H T T T T P2 : H H H H T Now when P1 will be flipped P1 : H H H H T P1(Heads) = P2(Heads)
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logicmathsimpleclean

There are several chickens and rabbits in a cage (with no other types of animals). There are 72 heads and 200 feet inside the cage. How many chickens are there, and how many rabbits?
There are 44 chickens and 28 rabbits in the cage. Let c be the number of chickens, and r be the number of rabbits. r + c = 72 4r + 2c = 200 To solve the equations, we multiply the first by two, then subtract the second. 2r + 2c = 144 2r = 56 r = 28 c = 44
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