Can you find the three digit code to open the number lock? You have five clues each based on a code combination. You have 5 minutes to solve the riddle.

### 3 digit Number lock puzzle with five clues including 154

Following are five clues on three-digit codes for a number lock. Use the clues to find the code for opening the lock.

**Clue 1: Code 154:** One digit is right and is in the correct place.

**Clue 2: Code 431:** One digit is right, but in the wrong place.

**Clue 3: Code 813:** Two digits are right and both are in correct place.

**Clue 4: Code 268:** One digit is right, but in the wrong place.

**Clue 5: Code 435:** Two digits are right, but both are in the wrong place.

From the clues, find the three-digit code that will open the number lock.

**Time to solve:** 5 minutes.

### Solution to the Number lock puzzle with clues including 154

First objective in solving a number lock riddle is to **eliminate incorrect digits** or **find correct digits**. But, *no clue alone can do either.*

**More than one clue are to be analyzed together.**- The clues should have
**one digit should appear in the clues with conflict in their position description.**

Following this idea, use **Clue 3 and Clue 1 together** to make the first breakthrough.

**Clue 1: Code 154:** One digit is right and is in the correct place.

**Clue 3: Code 813:** Two digits are right and both are in correct place.

**Analysis:**In first clue on 154, if 1 is right digit, its correct place is leftmost. Again, by the 3rd clue on 813, correct place for digit 1 is the middle position if the digit is right.**Both cannot be true.**

The only possibility is,

**Conclusion 1:**Digit 1 is a wrong digit.

Now look for a clue with the incorrect digit 1. In Clue 3, digit 1 appears, and it **helps to identify two correct digits at one go.**

**Clue 3: Code 813:** Two digits are right and both are in correct place.

**Conclusion 2:**As digit 1 is wrong,**digits 8 and 3 are the two right digits and are in the correct places.**The code is in the form of**“8 ? 3”.**Only the middle digit to discover.

*Third clue exhausted of its potential.*

#### Identification of the third correct digit to solve the number lock riddle

Consider the clinching Clue 1:

**Clue 1: Code 154:** One digit is right and is in the correct place.

- In Clue 1, the
**digits 1 and 4 in the leftmost and rightmost positions cannot be the right digits**as these are already occupied by correct digits 8 and 3 respectively. Both digit 1 and digit 4 are incorrect.

**Final conclusion:****Digit 5**is occupying the only available middle position and by the clue description it**must be the single correct digit in the code correctly placed.**

**The code to open the number lock is** **8 5 3**.

*The 4th and 5th clues stay unused.* **This is a measure of efficient solution**. The number lock riddle is solved using only first three clues.

You may verify the conclusions against these two clues.

### End note

The key to the quick solution of reasoning puzzles is to analyze the most effective clue individually or together with other clues.

To enjoy solving many more such number lock puzzles, click **here.**

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