A simple riddle many people miss - the watermelon paradox

Summary

In this intriguing video, Press Tow Walker presents a popular riddle involving watermelons with a water content of 99% that, after evaporation, drops to 98%. The challenge is to determine the final weight of the watermelons, which surprisingly turns out to be 50 kg, contrary to the initial intuitive guess of 99 kg. The video explores various methods to solve the puzzle, revealing a veridical paradox—a counterintuitive yet correct result—and encourages viewers to share the puzzle to witness others' surprising reactions.

Takeaways

• 🍉 The presented riddle involves watermelons with an initial water content of 99% that decreases to 98% by the time they reach their destination.
• 🚂 The watermelons were transported by train, and the weight change is the focus of the riddle.
• 📚 This riddle is a popular puzzle that has appeared in exams like KVPY in India and might be part of technical interviews.
• 🥔 The puzzle can also be framed with potatoes instead of watermelons, but the mathematical principle remains the same.
• 🤔 The initial intuitive answer of 99 kg is incorrect, which surprises many, including educated individuals with advanced degrees.
• 🎓 Even a group of MERS and PhD scientists initially got the puzzle wrong, highlighting the counterintuitive nature of the result.
• 📉 The correct answer is 50 kg, indicating a significant loss in weight when the water content drops from 99% to 98%.
• 📝 The script explains multiple methods to solve the puzzle, emphasizing the importance of careful mathematical reasoning.
• 🔢 The solution involves understanding that the 'dry' weight remains constant while the water weight changes as a percentage of the total weight.
• 🧩 The script uses algebraic equations to demonstrate that the final weight must be 50 kg, correcting the common misconception.
• 📊 A visual representation with dots is provided to illustrate why the final weight is 50 kg, making the abstract concept more tangible.
• 🎭 The riddle is referred to as a 'veridical paradox' because it yields an absurd or counterintuitive but correct result.

Q & A

What is the riddle presented in the video about?

The riddle is about a person who carried 100 kg of watermelons with an initial water content of 99%. After traveling by train, the water content dropped to 98%, and the question is to determine the final weight of the watermelons.

Why is the intuitive answer of 99 kg incorrect?

The intuitive answer of 99 kg is incorrect because it assumes that only 1 kg of water is lost, which would be 1% of the initial 100 kg. However, this doesn't account for the change in the proportion of water to the total weight.

What is the correct final weight of the watermelons after the water content drops?

The correct final weight of the watermelons is 50 kg, which is a surprising result given the initial assumption.

What is the term used to describe the type of paradox presented in the riddle?

The term used to describe this type of paradox is a 'veridical paradox', which is a result that is absurd or counterintuitive but is actually correct.

How does the video explain the incorrect reasoning behind the initial guess of 99 kg?

The video explains that the incorrect reasoning is based on the assumption that only 1 kg of water is lost, without considering that the remaining weight must also adjust to maintain the new water content percentage.

What is the initial water content of the watermelons in the riddle?

The initial water content of the watermelons is 99%.

What percentage does the water content drop to after the journey?

The water content drops to 98% after the journey.

What is the term used for the puzzle when it involves potatoes instead of watermelons?

The term used for the puzzle when it involves potatoes instead of watermelons is not specified in the script, but it is implied that the mathematics and the principle behind the puzzle remain the same.

What is the role of the 1 kg of 'other weight' in the riddle?

The 1 kg of 'other weight' represents the non-water content of the watermelons, which remains constant throughout the journey while the water content decreases.

How does the video script illustrate the correct answer of 50 kg?

The video script illustrates the correct answer by showing that if the final weight were 99 kg with 98% water content, it would create a contradiction. It then uses algebraic methods to solve for the final weight, which turns out to be 50 kg.

What is the significance of the 100 dots visual representation in the video?

The 100 dots visual representation is used to show the initial 100 kg of watermelons, with 99 dots representing the water weight and 1 dot representing the dry weight. As water evaporates, the dry weight remains, and the final total weight is recalculated based on the new water content percentage.