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January 2, 2009

8 Ball Problem

You have eight almost identical balls, but one of them is
a little bit lighter than the others. It is not that lighter,
though, that you can tell the difference by hand, but you
have a two-armed balance. How can you find the light
ball with only two measures?


Anirudh Tiwari said...

make a group of 3,3,2
1. Measure group of 3,3 on the balance.
case a. If two groups equal the defected ball is in group of 2. Go to step 2.
case b. If one of the group3 is heavy the other group of 3 conains the defected ball.Go to Step 3.

2. Measure the two balls you will get the defected. Your work is done. STOP

3. Distribute this group into further 3 groups of 1 ball each.
Measure any two balls
case a. If both are equal the third ball is the culprit. STOP
case b. If not equal then Step2 folows. STOP

You ve got the answer in 2 steps :
1-2 or 1-3

Anonymous said...

they could be lighter in colour you wouldnt need the balance.
So long as youre not colour blind its easy!

Sufyan Malik said...

if you have N balls and you have to find out heavier one , in how many steps it will be done, write solution