🧠 Bat and Ball Puzzle | Quick Maths Quiz Challenge
A short and surprising maths question
Maidin mhaith, quizzers! 👋 Welcome to the first post in our three-part mini-series exploring some of the world’s most deceptively simple — yet surprisingly tricky — logic puzzles. These brain teasers aren’t just fun challenges; they’ve been used in psychological research to investigate how we think, and especially how our quick instincts can sometimes mislead us.
This set of puzzles was originally created for the Cognitive Reflection Test, developed by Professor Shane Frederick at Princeton University. They have been given to students at prestigious universities such as MIT, Harvard, and Stanford, and most often trip people up! The trick is to override that first, automatic answer and think a little deeper.
Let’s start with one of the most well-known puzzles in this collection: the bat and ball problem. 🧩 It’s a classic logic teaser. Ready to slow down your thinking and avoid the common instinctive error?
Question: A bat and a ball together cost €1.10. The bat costs exactly €1 more than the ball. How much does the ball cost?
How to Solve
Method 1: Try it and see. Drumroll please… tap to reveal the answer!
This is a trial-and-error method — testing values until the difference is exactly €1.00.
- Bat: €1.00, Ball: €0.10 → Difference: €0.90 ❌
- Bat: €1.01, Ball: €0.09 → Difference: €0.92 ❌
- Bat: €1.02, Ball: €0.08 → Difference: €0.94 ❌
- Bat: €1.03, Ball: €0.07 → Difference: €0.96 ❌
- Bat: €1.04, Ball: €0.06 → Difference: €0.98 ❌
- Bat: €1.05, Ball: €0.05 → Difference: €1.00 ✅
Once the difference is exactly €1.00, we’ve found the correct answer.
Method 2: Solve a Linear Equation (Algebra). Tap here and bask in your brilliance (or not)!
Let’s say the ball costs x.
Then the bat costs x + €1.
So the equation becomes: x + (x + €1) = €1.10
That simplifies to:
2x + €1 = €1.10
Subtract €1 from both sides:
2x = €0.10
Divide both sides by 2:
x = €0.05
The ball costs €0.05, and the bat is €1 more: €1.05. Together they total €1.10. ✅
If your first thought was “€0.10”, don’t worry, you’re in good company. It’s the most common instinctive answer, but it’s not quite right.
This puzzle perfectly illustrates how our gut reactions can sometimes lead us astray, especially when numbers are involved and time is ticking. That’s why psychologists love using tests like this — they help us understand the quirks of human thinking, and where it can trip up.
Keep an eye out for Wednesday’s puzzle, where we’ll switch gears from algebra to a problem about machines, timing, and scale. Ready to stretch your reasoning in a whole new way? Thanks for joining in — agus slán go fóill!
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How did you get on? Got thoughts, scores, or reckon you’ve spotted something? Drop your comments below! ✍️
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