# Find the defective ball

## Find the defective ball

You have been given 12 balls. 11 of them have the same weight and the remaining one is heavier than others. Find the defective ball in minimum no. of weighing.

**Admin**- Admin
- Posts : 39

Join date : 2008-08-03

## am i rite?

First divide the balls in 6 each grp...weigh them....

one grp will have less wt..identify it...den again divide in 3 each..follow d same process.

now u hve to find out of 3 which has lower wt...den weigh any two...if dey r same d 3 one has less wt..or u hve t less wt ball directly....

all this process requires 3 time weighing...........

plz tell if am i rite??

one grp will have less wt..identify it...den again divide in 3 each..follow d same process.

now u hve to find out of 3 which has lower wt...den weigh any two...if dey r same d 3 one has less wt..or u hve t less wt ball directly....

all this process requires 3 time weighing...........

plz tell if am i rite??

**himadhav**- Posts : 1

Join date : 2008-08-11

## Re: Find the defective ball

We can do in one another way

We can take two sets of 5 balls each at random

(i)If the two sets have equal weights then the defective ball will be from the other two which can be known after one more try.

So 2 try's in this case

(ii)If one of the sets is heavier select 4 balls at random(sets of 2 each)and determine which is heavier.

If each set is equal then the remaining fifth ball is defective(2 try's)

(iii)Else if one of the sets of two balls is heavier than take the heavier set and compare the two balls directly

heavier will be defective

(3 try's in WORST CASE)(2 in OTHERS)

We can take two sets of 5 balls each at random

(i)If the two sets have equal weights then the defective ball will be from the other two which can be known after one more try.

So 2 try's in this case

(ii)If one of the sets is heavier select 4 balls at random(sets of 2 each)and determine which is heavier.

If each set is equal then the remaining fifth ball is defective(2 try's)

(iii)Else if one of the sets of two balls is heavier than take the heavier set and compare the two balls directly

heavier will be defective

(3 try's in WORST CASE)(2 in OTHERS)

**goldberg**- Posts : 8

Join date : 2008-08-11

## Re: Find the defective ball

This might be another solution....

DIvide that 12 balls in group of 4 balls .

compare any 2 group,if neone is heavier then we have defective in that grp,otherwise the remaining grp is heavier and contains defective ball.

then select any 2 balls frm that grp and compare if any one is heavier then ..that one is defective(2 times),otherwise in remaining 2 balls we have defective,and we require one comparision for finding defective(3 times).

DIvide that 12 balls in group of 4 balls .

compare any 2 group,if neone is heavier then we have defective in that grp,otherwise the remaining grp is heavier and contains defective ball.

then select any 2 balls frm that grp and compare if any one is heavier then ..that one is defective(2 times),otherwise in remaining 2 balls we have defective,and we require one comparision for finding defective(3 times).

**chunks**- Posts : 6

Join date : 2008-08-14

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