Capco
3.0 of 5
www.capco.com Edegem, Belgium 1000 to 5000 Employees

# CapcoAssociate Interview Question (student candidate)

I interviewed in San Bruno, CA and was asked:
"Let's say you have 10 bags of nails, and each nail weights 10g. You also have a scale upon which you can weigh a combination of the bags or nails from the bags once. You know that one of the bags is off by a certain amount of grams, but you don't know which bag or by how much. How do you find out, with one weighing, which bag it is?"
 Tags: brain teaser ,   See less 8

Part of a Associate Interview Review - one of 52 Capco Interview Reviews

3
of 7
Number the bags 1 through 10. Take 1 nail from bag 1, 2 nails from bag 2, and so on. Take those 55 nails, which should weight 550g, and place them on the scale. If the weight differs from 550g by a certain amount, then that tells you which bag it is and how much it's off by.
- Interview Candidate on Apr 25, 2010 Flag Response
3
of 6
If each "nail weights 10g" as posed in the problem the ONLY weight you will get is 550g.
My Idea is the instructions state "can weigh a combination of the bags or nails from the bags once." Place bag on scale result should = 100g, add bag 2 = 200g ect. when you add a bag and the result = less than the 100g, result = bag number and weight and difference. As you have continually adding weight is counts 1 time.
- EnrgyAR on Apr 28, 2010 Flag Response
1
of 7
Who cares? If you run out of nails go get some more.
- Bobba Louie on Apr 30, 2010 Flag Response
1
of 7
You guys are doing this wrong. This is a twist on a very old problem, that actually has to do with twelve balls and can use the scale only three times. The trick is to divide the bags into smaller groups of 3, and see in which direction the bags move. It's easier if you draw it out. It is from "games for the super intelligent" by James Fixx.
- takepanch on Apr 30, 2010 Flag Response
6
of 8
If I can only weight them once... then I'd put all the bags on, one weigh in and take the bags off one by one. The weight should go down by 10g each time until you get to the bag which is off. Technically it's one weigh in at the beginning and the rest are clearing the scale.
- fingers crossed on Apr 30, 2010 Flag Response
3
of 3
Take all the nails out of the bags weigh them divide by 10. The number wont come out even, bag up your nine even piles, then the last bag you have is the one that is "short".
- kgar79 on May 1, 2010 Flag Response
1
of 4
This is a stupid question to use in an interview. Presumably by the time people get to this level, they've already taken the SAT and GRE, the latter of which includes a logic section. Test people on things that are going to matter for the company's bottom line, not a logic problem.
- Anonymous on May 1, 2010 Flag Response
2
of 2
I agree with kgar 79. The problem states that you can weigh the nails individually, which means you can take them out of the bag. Once you do, you'll be able to see which bag has more or less nails than the others. Since the nails all weigh the same, any variation in weight, will be determined by whole nails.
- hc on May 4, 2010 Flag Response
1
of 3
Simple, and it can be done without weighing anything. Count the number of nails in a bag and multiply the number by 10g.
- Anonymous on May 4, 2010 Flag Response
1
of 1
vote
kgar79 got it right. Just dump out all the nails, put the same number of nails in nine of the bags,their weight is now 10g x the number of nails per bag, then put the rest of the nails in bag #10. Then weigh it and now you know which and by how much it is off.
You don't actually even need the scale.
- Noburo on May 5, 2010 Flag Response

### Salaries by Company

Tags are like keywords that help categorize interview questions that have something in common.

Glassdoor is your free inside look at Capco interview questions and advice. All interview reviews posted anonymously by Capco employees and interview candidates.