Few more brain teasers if you really think they can tease you
Disclaimer: None of the puzzles are mine. I am just writing them down so people can read it.
Puzzle:
you are playing a coins game with your friend. there are total of 100 coins on the table. At any playing turn, the player has to pick minimum 1 coin and can pick maximum of 8 coins. last one to pick the coins from the table wins. if you are given a chance to pick first can you win?
Now when we look at the puzzle above the total number of coins are 100 and I can pick up anything in the range of 1 to 8. Does that guarantee me the win? We being humans normally think on the forward way. Here is the way when we have a goal in mind can we think in reverse direction and come with a solution.
there are only three rules in the game above.
1) last one picking up the coins win
2) you have to pick the coins all the time
3) you have to restrict your opponent from winning
if you look at the the third rule, that's the whole point of this game. Given a goal how can you achieve it?
so lets think in a reverse manner.
To win I will need to pick up the last coins from the table. I can pick maximum of 8 and minimum of 1 coin.
so that means as long as I leave the second last turn on 91, I will win.
Ok how do I make sure that I will have someone reach 91. Now instead of having 100 coins lets say we just have 91 coins in total. In that case the second last turn becomes 82.
so if we put down the numbers in this series they look something like this
91 82 73 64 55 .....10 1
now if want to put a formula around it
(max + min)X playing turn + 1 will guarantee me the win
so now the first aim is not 100 .. first aim is make sure that when the next player plays you need to keep these many coins of the table
so now can solve the puzzle above
==================================================================
Puzzle:
This is normal puzzle known to all. .
There are three lions and three humans on the bank of a river. You have to take them across the river on the other bank. You are the only allowed person who can row the boat across the river. At any time you can let the number of lions exceed the number of humans else they will eat the human. You will need to carry at least one passenger in any direction you travel. How will you transport them?
Lets represent Lions as L, Humans as H and then do the transportation
HHH LLL
HHHLLL
-----HL----->
HL
<-----H-----
HHLL L
-----HL----->
HHL HLL
<----L-------
HHLL HL
----HL----->
HL HHLL
<----L-------
HLL HHL
----HL------>
L HHHLL
<----H------
HL HHLL
-----HL---->
HHHLLL
==================================================================
Puzzle:
Find the minimum number of cuts you will need to make in cheese cube to generate 27 cubes?
try two cuts across each side of the cube which is not cut. So on the top, on the side and horizontally.
minimum of 6 cuts. Mathematically if you try you can not do in 2^4=16, ie in 4 attempts. So you may suggest 5 but that would be wrong)
===================================================================
Puzzle:
Using a 4 minute hourglass and 7 minute hourglass measure 9 minutes
Disclaimer: None of the puzzles are mine. I am just writing them down so people can read it.
Puzzle:
you are playing a coins game with your friend. there are total of 100 coins on the table. At any playing turn, the player has to pick minimum 1 coin and can pick maximum of 8 coins. last one to pick the coins from the table wins. if you are given a chance to pick first can you win?
Now when we look at the puzzle above the total number of coins are 100 and I can pick up anything in the range of 1 to 8. Does that guarantee me the win? We being humans normally think on the forward way. Here is the way when we have a goal in mind can we think in reverse direction and come with a solution.
there are only three rules in the game above.
1) last one picking up the coins win
2) you have to pick the coins all the time
3) you have to restrict your opponent from winning
if you look at the the third rule, that's the whole point of this game. Given a goal how can you achieve it?
so lets think in a reverse manner.
To win I will need to pick up the last coins from the table. I can pick maximum of 8 and minimum of 1 coin.
so that means as long as I leave the second last turn on 91, I will win.
Ok how do I make sure that I will have someone reach 91. Now instead of having 100 coins lets say we just have 91 coins in total. In that case the second last turn becomes 82.
so if we put down the numbers in this series they look something like this
91 82 73 64 55 .....10 1
now if want to put a formula around it
(max + min)X playing turn + 1 will guarantee me the win
so now the first aim is not 100 .. first aim is make sure that when the next player plays you need to keep these many coins of the table
so now can solve the puzzle above
==================================================================
Puzzle:
This is normal puzzle known to all. .
There are three lions and three humans on the bank of a river. You have to take them across the river on the other bank. You are the only allowed person who can row the boat across the river. At any time you can let the number of lions exceed the number of humans else they will eat the human. You will need to carry at least one passenger in any direction you travel. How will you transport them?
Lets represent Lions as L, Humans as H and then do the transportation
HHH LLL
HHHLLL
-----HL----->
HL
<-----H-----
HHLL L
-----HL----->
HHL HLL
<----L-------
HHLL HL
----HL----->
HL HHLL
<----L-------
HLL HHL
----HL------>
L HHHLL
<----H------
HL HHLL
-----HL---->
HHHLLL
==================================================================
Puzzle:
Find the minimum number of cuts you will need to make in cheese cube to generate 27 cubes?
try two cuts across each side of the cube which is not cut. So on the top, on the side and horizontally.
minimum of 6 cuts. Mathematically if you try you can not do in 2^4=16, ie in 4 attempts. So you may suggest 5 but that would be wrong)
===================================================================
Puzzle:
Using a 4 minute hourglass and 7 minute hourglass measure 9 minutes
| step | 4 minute | 7 minute | TIME |
| 1 | FLIP | FLIP | 0 |
| 2 | FLIP | 3 minutes remaining | 4 minutes |
| 3 | 1 minute remaining | FLIP | 7 minutes |
| 4 | 0 | FLIP | 8 minutes |
| 5 | 0 | 0 | 9 minutes |
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