All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Logic > Weights and Scales
Wrenches (Posted on 2004-07-02) Difficulty: 2 of 5
There are 4 wrenches just unpacked from a box. They all look the same. There might be one defective item which is either heavier or lighter. Fortunately there is a fifth one that is standard. If you can use a scale to weigh only 2 times, can you find out:
  1. Is there a defective wrench?

  2. If there is a defective item, is it heavier or lighter?

See The Solution Submitted by Brian Smith    
Rating: 2.8333 (6 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Some Thoughts Solution | Comment 1 of 13

This seems simple, which probably means I'm approaching it incorrectly.

First, we assume we don't know the weight of the standard wrench, and just that it's a standard. The first weighing then is to determine the exact weight of the standard.

Second, we weigh together all four of the wrenches in question. If the weight is exactly four times that of the standard, there is no defect. If it is greater than four times the standard, there is a heavier wrench. Similarly, if it is less than four times the standard, there is a lighter wrench.


  Posted by Eric on 2004-07-02 09:17:57
Please log in:
Login:
Password:
Remember me:
Sign up! | Forgot password


Search:
Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (3)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2017 by Animus Pactum Consulting. All rights reserved. Privacy Information