[Riddle] Two Ropes and 45 Minutes

💨 I might suffocate at this rate...

🕯️ Scenario

A cold voice emerges from the speaker:
"Measure exactly 45 minutes. Fail, and the oxygen supply will be cut off."

On the table, there are two ropes and a box of matches.

📜 Instructions

• Each rope takes exactly 1 hour to burn completely.
• The ropes do not burn at a uniform rate (some parts may burn faster or slower).
• Using conventional methods, measuring exactly 45 minutes is impossible.

💡 How Can You Measure Exactly 45 Minutes?

The key to solving this puzzle lies in using the uneven burning of the ropes strategically. Here’s the step-by-step solution:

✅ Solution

Step 1: Ignite One Rope from Both Ends & The Other from One End

• Light both ends of the first rope at the same time.
• Light one end of the second rope at the same time.
• The first rope will completely burn in 30 minutes (since burning from both ends halves the time).

Step 2: When the First Rope Burns Out (30 Minutes Have Passed)

• At this moment, the second rope has been burning for 30 minutes from one end.
• Since the second rope originally takes 1 hour to burn, it still has 30 minutes’ worth of material left to burn.
• Now, light the other end of the second rope.

Step 3: The Second Rope Burns Out (Total Time = 45 Minutes)

• Since the second rope is now burning from both ends, it will take only 15 more minutes to completely burn out.
• Total time elapsed: 30 minutes + 15 minutes = 45 minutes.

🔍 Why Does This Work?

Because burning from both ends effectively doubles the speed of combustion, we can manipulate the ropes to track precise intervals:

• First rope: 60 minutes → Burn from both ends → Burns in 30 minutes
• Second rope:
  • First 30 minutes: Burns normally from one end
  • Remaining portion (30 minutes worth): Burns from both ends, reducing the time to 15 minutes

Thus, the total elapsed time is 45 minutes, ensuring a perfect measurement!

🔥 Mission accomplished! 🔥