Three friends go out for dinner and receive a bill of 30 BTC, so they each chip in 10 BTC (3 × 10 = 30 BTC).
Later, the waiter realizes the actual bill was only 25 BTC.
To fix the overcharge, he decides to return 5 BTC to the group. But since it's tough to split 5 BTC evenly among three people, he gives 1 BTC back to each friend (3 × 1 = 3 BTC) and keeps 2 BTC as a tip.
Now each friend has effectively paid 9 BTC (10 - 1), totaling 27 BTC (3 × 9).
Add the 2 BTC tip, and it seems to make 29 BTC…
But wait — they originally paid 30 BTC!
Where’s the missing 1 BTC?! 🤯
🧩 Hint: It’s not a math error — it’s a classic logic trap.
The trick is in how the numbers are framed. 😉
