Problem: 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.
This puzzle was asked in Yahoo Interview.
Solution:
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)
That time head count is zero that is also valid answer
What if first pile has 3 heads and 2 tails and second pile has vice versa!
Still the same
it still works. whats the problem
You can also flip them all over to the same side but two and then separate the coins into two equal piles splitting the two odd sided coins, one in each pile. This too would ensure that the two piles have equal numbers of heads either 1 or 4.
How can you do that blind folded ?
Hello
what if first pile is made => H,H,H,H,H
second pile => T,T,T,T,T
If first pile is reversed, then first pile => T,T,T,T,T and second pile => T,T,T,T,T
There is no perfect answer to this question.
However worst case 2 questions can be asked to the person who sees the piles and confirmes if OK or not.
e.g if we replace first pile wrong then if we got the answer as wrong.
then we can reverse first pile as before and do the replacement of second one.
so 2 trials worst case.
The question is “How do you make two piles of coins each with the same number of heads up?”
In your scenario flipping pile 1 results in both sides now having 0 heads, meaning both sides have the same number of heads up.
What if the pile’s 1st order s set to- TTHTT
and the order one – HHTHH
then how it will be solved..
You are allowed to touch the coin. On the basis of structure you feel put then in one pile .
good
10 Coins – Blindfolded Interview Puzzle Answer
https://www.youtube.com/watch?v=sIiiaifB8aI