Friday, November 26, 2010

How many weights? - One puzzle a day - Puzzle Buddies

Puzzle: You have a common balance with two sides. You can only keep weighs on one side. You have to weigh  items from 1 to 1000 weight units with integral weights only.
What is the minimum number of weights required and what will be their weights?
Eg. With 2 weights one of 1 weight unit and other of 3 weight unit you can measure 1, 3 and 4 only.
Note: Don't forget to visit us again. Answer to the puzzle will be posted tomorrow.  You can provide your answer in comments.

Solution: This puzzle is an easy puzzle as to make any odd number you need all other even numbers and one 1.
So only one odd number is needed to make all odd numbers. Now you are left with all even numbers. All even numbers are base 2 and thus can be though of as binary representation. To make 1000 you need at most 10 bits(1111101000). You can make any number below 1000 from these bits.
So the answer is 10 weights required. 1, 2, 4, 8,16, 32, 64, 128, 256, 512.
Winner: Kasturi is again the winner.

2 comments:

  1. We need 9 weights. 1, 2, 4, 16, 32, 64, 128, 256 and 512.

    ReplyDelete
  2. Forgot 8 :-)
    Its 10 weights: 1,2,4,8,16,32,64,128,256,512.

    ReplyDelete