top button
Flag Notify
    Connect to us
      Facebook Login
      Site Registration

Facebook Login
Site Registration

How could you find the box with 9 kgs balls with just 1 weighing?

+1 vote

There are 10 identical boxes each containing 10 balls. One Of the box has all the balls of 9 kgs while rest of the boxes have balls of 10 kgs. You have an electronic weighing machine. How could you find the box with 9 kgs balls with just 1 weighing?

posted Dec 17, 2014 by Shashi Kant

Share this puzzle
Facebook Share Button Twitter Share Button LinkedIn Share Button

1 Answer

+3 votes
Best answer

For convenience sake, let’s name the boxes from 1 to 10. In order to solve this problem, you have to leverage the fact that you know exactly what each good ball is supposed to weigh and what each defective ball is supposed to weigh. Many of us instinctively will take one ball out of each box and try to find a way to make it work but the trick to take different number of balls from each box.

The number of balls you pick from each bag is equal to the box number. For example, pick 1 ball from box 1, 2 balls from box 2 and so on. In total you will have 55 balls. If all of the boxes have good balls, then the total weight of these balls would be 550KG.

If box 1 has defective balls, then the total weight should be 1gm less than expected (only one ball weighing 9 kg). If box 2 has defective balls, then the total weight should be 2KG less than expected (two balls weighing 9 kg). So once you weigh the set of chosen balls, find out the difference between the total weight and the expected weight. That number represents the box number which contains the defective balls.

answer Dec 17, 2014 by Cedric Grigory
Nicely explained

Similar Puzzles
0 votes

You have 5 jars of pills. Each pill weighs 10 grams, except for contaminated pills contained in one jar, where each pill weighs 9 grams. Given a scale, how could you find which jar had the contaminated pills in just one measurement?

0 votes

A box contains 4 red balls, 6 green and 8 black balls. Three balls are drawn at random find the probability that three balls are of different color?

0 votes

enter image description here

Assume the given figure to be a delicious doughnut. Yes, now you can concentrate more on the puzzle. So you have this delicious doughnut in your refrigerator when your friends come knocking at the door. There are eight of them.

Now you have to make three cuts in this doughnut so that each one of you nine people can enjoy a piece of it. Neither you nor your friends would mind the size of their piece as long as they are getting it.

How will you do it?

0 votes

You have 2 balls with identical diameter and weight. One is solid, one is hollow. You can't tell by knocking on them. How can you find the solid one?

Contact Us
+91 9880187415
#280, 3rd floor, 5th Main
6th Sector, HSR Layout
Karnataka INDIA.