Monday Morning Braintease - Probability

I apologize for the late post, I usually like to try to get these out in the morning...hence the name.

You have an object whose weight is an integer value somewhere between 1 and 100 and a balancing scale. What is the fewest number of weights you need to be guaranteed that you can correctly identify the weight of the object?

x
x
x
x
x
x
x
x
x
x
x
x
x
x
edit: (extra spaces added so everyone that is trying to solve the brainteaser doesn't immediately see the answer)

Comments (7)

Jul 9, 2012

Seven, if I understand the question correctly.

    • 1
Jul 9, 2012
Downeasta:

Seven, if I understand the question correctly.

Same

2^x = 100 --> x = 6.644 --> x = 7

    • 1
Jul 9, 2012

+1 each. more bananas for anyone that can explain the thought process better, or come up with a better solution??

Jul 9, 2012

Buddyfox, can you post like 5 times after the original post so upon opening the page everyone doesn't see the answer...

Jul 9, 2012
HFFBALLfan123:

Buddyfox, can you post like 5 times after the original post so upon opening the page everyone doesn't see the answer...

Good Idea, I will do this going forward.

Jul 9, 2012

Let x = 100

  1. Choose 50
  2. Choose 75
  3. Choose 87
  4. Choose 93
  5. Choose 96
  6. Choose 98
  7. Choose 99

As you notice each time I keep halving the number.

Let x = 16.
1. Choose 50
2. Choose 25
3. Choose 13
4. Choose 19
5. Choose 17
6. Choose 15
7. Choose 16 for shits'n'gigs.

Robert Clayton Dean: What is happening?
Brill: I blew up the building.
Robert Clayton Dean: Why?
Brill: Because you made a phone call.

    • 1
Jul 9, 2012
Comment
    • 1