Puzzle Archives - Puzzle Prime

Clean Death

Section: Brain Teasers Category: Science

Difficulty: Hard

A man was going to bleach his socks because they had gotten muddy the day before. As he was pouring the bleach into the washing machine, he spilled some on the floor. He got some cleaning fluid and mopped it up with a rag. Minutes later he was dead. What killed him?

SOLUTION

When the ammonia (NH₃), found in cleaning fluids, is mixed with bleach (a dilute solution of sodium hypochlorite, NaOCl), a deadly gas (monochloramine, NH₂Cl) is produced that can kill a person instantly. The resulting chemical reactions are the following:

Bleach decomposes, forming hydrochloric acid and subsequently chlorine gas:
NaOCl → NaOH + HOCl
HOCl → HCl + O
NaOCl + 2HCl → Cl₂ + NaCl + H₂O
The chlorine gas reacts with the sodium hypochlorite in the bleach, releasing chloramine as a vapor:
2NH₃ + Cl₂ → 2NH₂Cl

Unknown Author March 25, 2023

3 Comments

In This Shoe…

Section: Brain Teasers Category: Deduction

Difficulty: Advanced

Fill the three missing numbers (using words) in the shoe below.

Remark: The missing words can be of any length.

SOLUTION

You should fill the words FIVE, THREE, FOUR to get:

“In this shoe, there are five H’s, three O’s, and four T’s.”

Unknown Author March 22, 2023

0 Comments

The Geography Quiz

Section: School Category: Quiz

Puzzle Prime March 19, 2023

0 Comments

Bicycle Tracks

Section: Brain Teasers Category: Detective

Difficulty: Advanced

You are chasing a criminal riding a bicycle, and you find his tracks left in the dirt. By investigating the tracks, can you determine which direction the criminal has fled to: left or right?

SOLUTION

The front wheels of the bicycle are traveling more distance and making sharper turns. Thus, the red tracks (as shown on the image below) correspond to the front wheel, and the green tracks correspond to the back wheel.

Then, since the back wheel is always pointing towards the front wheel, we conclude that the bicycle is moving towards the right.

Unknown Author March 16, 2023

2 Comments

The Pi Quiz

Section: School Category: Quiz

Puzzle Prime March 13, 2023

1 Comment

Terrible Rebuses 1

Section: Casual Puzzles Category: Rebus

Difficulty: Advanced

Recognize the phrases depicted by the “terrible rebuses” below.

SOLUTION

No use over spilled milk.
Two wrongs don’t make a right.
The squeaky wheel gets the grease.
When there is a will, there’s a way.

Etheo March 10, 2023

0 Comments

STANDARD Word

Section: Brain Teasers Category: Insight

Difficulty: Hard

Given the word STANDARD, take away two letters and then add three digits to make a logical sequence.

SOLUTION

Remove the two letters A to get ST-ND-RD and then add the digits 1, 2, 3 to get 1ST-2ND-3RD.

Unknown Author March 7, 2023

0 Comments

Tastes Better Than It Smells

Section: Casual Puzzles Category: Riddle

Difficulty: Easy

What tastes better than it smells?

SOLUTION

The answer is TONGUE.

Unknown Author March 4, 2023

0 Comments

Toasting Bread

Section: Brain Teasers Category: Deduction

Difficulty: Medium

Your toaster is broken, so you decide to toast your bread in a pan. The pan can hold three slices of bread at a time and takes 1 minute to toast one of their sides. How much time would it take you to toast four slices of bread on both sides using the pan?

SOLUTION

It would take you 2 minutes and 40 seconds. Label the slices with A, B, C, D, their top sides A1, B1, C1, D1, and their bottom sides A2, B2, C2, D2.

Toast A1, B1, C1 for 40 seconds.
Toast A2, B2, D1 for 40 seconds.
Toast A1, C2, D2 for 20 seconds.
Toast A2, C2, D2 for 20 seconds.
Toast B1, C1, D1 for 20 seconds.
Toast B2, C2, D2 for 20 seconds.

Unknown Author March 1, 2023

0 Comments

FEATURED

Puzzle Tournament 4

Section: Contests Category: Tournament

Tags: Featured

Puzzle Prime’s fourth puzzle tournament was organized on February 26, 2022. Congrats to REDCROUTONS who solved all the puzzles (even found a small mistake in one of them)!

You have 60 minutes to solve 6 puzzles, each worth 1 point. Upload your solutions as a pdf, document, or image, using the form below. Good luck!

Time for work: 1 hour

Each problem is worth 1 point. Use the form at the bottom of the post to send your solutions.

1. The Grid

by Puzzle Prime

Figure out how the last portion (7×5 in yellow) of the grid should be colored in black and white.

2. Hexado

by Dr. DJ Upton

Place arrows along hexagon edges so that the number of arrows pointing to each hexagon equals the number of dots inside, adhering to the following rules:

Arrows cannot be touching.
Arrows cannot be placed on dashed edges.

SHOW EXAMPLE

3. Segments

by Puzzle Prime

Use at most 27 segments to create the largest number with distinct digits.

Notes: For example, the number 273914 would use 5+3+5+6+2+4=25 segments.

4. Constellations

by Raindrinker

Connect the stars with lines, so that the number inside each star corresponds to the number of lines connected to it, and the number outside each star corresponds to the total number of stars in its group.

Note: No line connecting two stars can pass through a third star.

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5. Chess Connect

by Puzzle Prime

The starting and ending positions of 6 chess pieces are shown on the board. Find the trajectories of the pieces, if you know that they do not overlap and completely cover the board.

Notes: The pieces can not backtrack. Two trajectories can intersect diagonally but can not pass through the same square. Only the Knight has a discontinuous trajectory.

SHOW EXAMPLE