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.
Know how to solve difficult problems easily without wasting time on random attempts
Our ebook on puzzle solutions by innovative methods will show you just that.
Puzzles for Adults: 50 Brain Teasers with Step-by-Step Solutions: Boost Your Power of Problem Solving
BUY the eBook Amazon Kindle version here, from Google Play here and Paperback here.
Second book on Innovative Solutions to Matchstick Puzzles from Suresolv
BUY Creative Matchstick Puzzles Innovative Solutions eBook Amazon Kindle version
BUY the paperback here.
Puzzles you may enjoy
Easy to hard brain teasers with systematic solutions
Challenging brain teasers with solutions: Long list.
This will always be the most up-to-date full list with the brain teasers classified into categories that can be browsed separately.
You may also click on the category term link below to enjoy the brain teasers that are classified in the present category.
For example, if the category term link shown below is "Riddle", click on it to go through all the Riddles.