The Blindfolded and 10 Coins Puzzle is a classic logic riddle that tests your ability to think creatively and mathematically. In this puzzle, you are given 10 coins, 5 with heads facing up and 5 with tails. However, you are blindfolded, so you cannot see or feel which side is up. The challenge is to divide the coins into two groups so that each group has the same number of heads.
This puzzle is often used in IQ tests, logical reasoning challenges, and brain teasers because it encourages thinking outside the box and using mathematical properties of coins and flipping.
Blindfolded and 10 Coins Puzzle Setup and Rules
Here’s how the puzzle works:
- You are given 10 coins, 5 heads and 5 tails.
- You are blindfolded, so you cannot identify the coins’ faces.
- The goal is to divide the coins into two groups such that both groups have the same number of heads.
- You can flip any number of coins but cannot peek.
The question:
How can you guarantee both groups have the same number of heads without seeing the coins?
How to Solve the Blindfolded and 10 Coins Puzzle?
This puzzle may seem impossible at first, but there is a clever and logical method using coin flipping properties.
Step 1: Divide the Coins into Two Groups
Randomly divide the 10 coins into two groups of 5 coins each.
- It doesn’t matter which coins are in which group.
- You do not need to know which are heads or tails at this point.
Step 2: Flip All Coins in One Group
Choose one group of 5 coins and flip every coin in that group.
- Again, it doesn’t matter which group you choose.
- Flip all 5 coins in the group.
Step 3: Why This Strategy Works
This method works because of the mathematical effect of flipping coins:
- Let the first group have X heads (X can be 0–5).
- Since there are 5 heads in total, the second group must have 5 – X heads.
- When you flip all coins in the first group:
- Each head becomes a tail, and each tail becomes a head.
- Therefore, the first group now has 5 – X heads.
Now, both groups have exactly 5 – X heads, meaning the number of heads in each group is equal.
Example:
- Suppose the first group originally had 2 heads and 3 tails.
- After flipping, the first group becomes 3 heads and 2 tails.
- The second group, which originally had 3 heads, still has 3 heads.
- Now both groups have 3 heads each, achieving the puzzle’s objective.
Visual Summary:
| Step | Action | First Group (Heads/Tails) | Second Group (Heads/Tails) |
|---|---|---|---|
| 1 | Randomly divide 10 coins | X / 5 – X | 5 – X / X |
| 2 | Flip all coins in one group | 5 – X / X | 5 – X / X |
| 3 | Check result | Equal heads in both groups | Equal heads in both groups |
Final Answer
To solve the Blindfolded and 10 Coins Puzzle:
- Divide the 10 coins into two groups of 5 coins each.
- Flip all 5 coins in one of the groups.
This ensures both groups have the same number of heads, regardless of the initial arrangement.
Why the Blindfolded and 10 Coins Puzzle is Popular?
This puzzle is widely used because it demonstrates how logic and mathematical thinking can solve seemingly impossible problems. It’s especially useful in:
- Logical reasoning tests
- IQ challenges and brain teasers
- Interviews for problem-solving roles
It teaches that strategy and clever manipulation can overcome limitations like not being able to see the coins.
Similar Logic Puzzles with Answers
1. The 100 Prisoners Hat Puzzle – Parity Strategy
Setup: 100 prisoners must guess their hat colors.
Answer: Using parity logic, 99 prisoners are guaranteed survival, sometimes all 100.
2. The River Crossing Puzzle – Farmer, Goat, Wolf, and Cabbage
Setup: Transport a goat, wolf, and cabbage across a river safely.
Answer: Sequence the crossings strategically to avoid any item being eaten.
3. The Monty Hall Problem – Probability Choice
Setup: Three doors, one hides a car. Switch or stay?
Answer: Switching increases the odds of winning from 1/3 to ⅔.
4. The Two Doors Riddle – Truth and Lies
Setup: Two guards, one lies, one tells the truth.
Answer: Ask what the other guard would say, then choose the opposite door.