Advanced – Page 15 – Puzzle Prime

Flow Maze

Section: Casual Puzzles Category: Maze

Difficulty: Advanced

Enter the maze, pass through all yellow circles, then leave the maze. Go only the flow, not shard turns.

SOLUTION

The solution is shown below.

Dave Phillips May 25, 2019

0 Comments

How many moves?

Section: Brain Teasers Category: Chess

Difficulty: Advanced

If Black just made a move in this game, what is the minimum amount of moves that have been played?

SOLUTION

8 moves example:

1. f3 Nf6
2. Kf2 Ng8
3. Ke3 Nf6
4. Kd3 Ng8
5. Ke4 Nf6
6. Ke3 NNg8
7. Kf2 Nf6
8. Ke1 Ng8

In order to see that 8 is the minimum number of moves, notice that Black could only move rooks and knights, and therefore he has made an even number of moves. This implies that White has made an odd number of moves, excluding the pawn on f3. This is possible only if he has placed his king on a white cell at some point and then returned it back to e1, which would take at least 8 moves.

John Beasley April 28, 2019

0 Comments

Gunshots

Section: Brain Teasers Category: Detective

Difficulty: Advanced

Two gunshots were fired through the window of a coffee shop. When the police arrived, they successfully recognized which gunshot was fired first. Which was the first gunshot and how did they figure that out?

SOLUTION

The cracks of the left gunshot end up right at the cracks of the right gunshot. Therefore the first gunshot is the one on the right.

Unknown Author April 25, 2019

1 Comment

Six Coins

Section: Brain Teasers Category: Practical

Difficulty: Advanced

Take six coins and arrange them in a triangle as shown in the image. Your goal is to rearrange the coins into a hexagon with only four moves. Every move consists of sliding one coin to a new location where it touches at least two other coins.

SOLUTION

The solution is shown below.

Unknown Author April 18, 2019

6 Comments

Short Friends

Section: Brain Teasers Category: Lateral

Difficulty: Advanced

Two very short friends, John and Jack, were living together in an apartment. Since they used to lose their apartment key very often, they decided to leave it on top of the door frame when they leave home. In order to reach the key, John was climbing on Jack’s shoulders and thus taking it down from the frame. However, John was the taller and the heavier guy of the two. Why didn’t Jack climb on top of his shoulders instead?

SOLUTION

The reason is that as being taller, John also had longer arms. If Jack climbed on John’s shoulders, he wouldn’t have reached the key.

Unknown Author April 5, 2019

2 Comments

Mate in 17

Section: Brain Teasers Category: Chess

Difficulty: Advanced

White to play and mate in 17 moves.

SOLUTION

e3 Rxe3
c3 Rxc3
Ka2 Ra3+
Kb1 Ra1+
Kc2 Rc1+
Kd3 Rc3+
Ke2 Re3+
Kf1 Re1+
Kg2 Rg1+
Kf3 Rxg3+
Ke2 Re3+
Kd1 Re1+
Kc2 Rc1+
Kb3 Rc3+
Ka2 Rxc7
Rh8+ Rc8
Rxc8#

Unknown Author March 21, 2019

3 Comments

Stones on a Chessboard

Section: Brain Teasers Category: Mathematics

Difficulty: Advanced

You place two stones on a chessboard and start moving them one by one, every time shifting a stone to an adjacent cell – left, right, up, or down, without letting the stones at any time occupy the same cell. Is it possible to find such a sequence of moves, that all possible combinations for the position of the stones occur exactly once?

SOLUTION

No, such sequence does not exist. Call a position of the stones “matching” if the stones occupy cells of the same color, and “opposite” if the stones occupy cells of opposite colors. If such sequence exists, then the number of matching and opposite positions must differ by at most 1. However, the number of matching positions is 64×31, whereas the number of opposite positions is 64×32, so this is not true.

Unknown Author February 28, 2019

0 Comments

The Temple of Doom

Section: Brain Teasers Category: Deduction

Difficulty: Advanced

You and eight of your team members are trying to escape the Temple of Doom. You are running through a tunnel away from a deadly smoke and end up in a large hall. There are four paths ahead, and exactly one of them leads to the exit. It takes 20 minutes to explore any of the four paths one way, and your group has only 60 minutes until the deadly smoke suffocates you. The problem is that two of your friends are known to be delirious and it is possible that they do not tell the truth, but nobody knows which ones they are. How should you split the group and explore the tunnels, so that you have enough time to figure out which is the correct path and escape the temple?

SOLUTION

You explore the first path. You send two of your teammates to explore the second path. You send the remaining six teammates in groups of three to explore each of the two remaining paths. If your path leads to the exit, then everything is good. Otherwise, you ask the two groups of three whether their paths lead to the exit. If in both groups everyone answers consistently, then nobody is lying, and you will escape. If in both groups there is a person whose answer is different from the others in the group, then the majority in both groups says the truth. Once again, you will know which path leads to the exit. Finally, if in exactly one of the groups everyone answers consistently, you ask the group of two. If the team members there answer consistently with each other, then they say the truth. You will have two groups which tell the truth and will know which path leads to the exit. If the answers of the teammates in the group of two differ, then in the inconsistent group of three the majority will be saying the truth. Again, you will be able to deduce which path leads to the exit.

Unknown Author February 28, 2019

14 Comments

FEATURED

Front Wheels

Section: Brain Teasers Category: Science

Difficulty: Advanced Tags: Featured

When a car is making a turn, are its front wheels parallel to each other?

SOLUTION

The front wheels are not parallel to each other. The reason is that when steering, all wheels are turning along arks that have a common center. Otherwise, the car would be drifting.

Unknown Author February 21, 2019

1 Comment

FEATURED

Six Friends Camping

Section: Brain Teasers Category: Lateral

Difficulty: Advanced Tags: Featured

Monday, six friends went camping. Tuesday, John, Jack, and James cooked some mushrooms. Wednesday came and they ate the mushrooms. Thursday found them dead. Exactly one friend survived, how come?

SOLUTION

The six friends are called John, Jack, James, Tuesday, Wednesday, and Thursday. John, Jack, James, and Tuesday cooked the mushrooms. Wednesday joined them and they ate the mushrooms. Thursday was the one to find them dead, so he is the survivor.

Puzzle Prime February 5, 2019

2 Comments