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.

### Open the lock riddle with 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 Open the lock riddle with clues including 154

Clue 1 by itself cannot help in decision, but use Clue 3 and Clue 1 together to make the first breakthrough.

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.

From clue 3 on 813, make the **second important conclusion,**

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.

In the second clue on 431 (which says, one digit is right but in the wrong place), the right digit is 3 and a wrong digit is 1. Thus resolve,

Conclusion 3:The digit 4 (apart from 1) is the second wrong digit.

It follows from clue 1 on 154,

Conclusion 4:As both 4 and 1 are wrong digits, digit 5 must be the third unknown digit. And it sits in the right middle position.

**Answer:** *The code is 853.*

The 4th and 5th clues stay unused. You may verify the conclusions using the 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.

Occasionally, a reasoning puzzle is solved without using a few conditions. It shows high efficiency of processing the clues.

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