8 balls

Question:

There are 8 balls. 7 of them weigh the same. 1 of them has a different weight, (you don’t know if it’s heavier or lighter). How do you find the odd ball with 2 weighs?

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.

C

A

P

T

A

I

N

I

N

T

E

R

V

I

E

W

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Solution:

Use an equilateral triangular lamina which is of uniform mass throughout.
It is balanced on a pole or a similar structure.

Steps: Place 2 balls at each corner (total 6 balls)

i. if the odd ball is one of those, one side will either go up or go down. Now repeat the process with one ball at each corner including the 2 unbalanced ones.

ii. if the balance is perfect, repeat the process with the remaining two balls and one of the already weighed balls.

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