Help >> Needed !!

[shahnaz]

Hi to you all


Try to help me in this one >>


You have 12 marble balls. There is only one odd ball, which you don't know if its heavier or lighter. You have a scale (one of those old school scales with two trays). You can use the scale 3 times . Can you find the odd ball? and How?

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I have tried but :(

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Hope You can Help Me >>

:think:

[© MATCHLESS]

Divide the 12 balls into three groups ..

so there will be 4 balls on every group


1st step
Put 2 groups on the 2 sides of scale and one out side

From this try you should know which group have the odd ball.

2nd step

now you have 4 balls, one of them is your target ball
put one ball on each side of the scale and keep 2 with you
if scale is equal then the odd ball is one of the 2 ball with you

3rd step

put one ball on each side of the scale and find the odd ball

:banana: :banana:

[shahnaz]

Hi >>> Abu Ghadah .. :)

It is a bit more complicated! unfortunately

However, here is the solution:



Divide the balls into three groups of 4.
Compare two groups.
If equal, then we know that the odd ball is among the other 4 balls, so do the following:
Place three balls from this group on one side and three balls from the others (For sure are normal) on the other side.
If they balance, then the odd ball is the forth ball of the group which we haven't placed on the scale.
If they don't balance, we know that the odd ball is one of the three balls and we know that it is heavier or lighter.
We place one ball on a side and another on the other side, if they balance then the third one is the odd, if they don't balance, then the odd ball is the one that is heavier or lighter depending on the result in step c.
If they are not equal, then we have 4 balls in one group (Group A) that are suspected to have the odd ball among them and to be heavier, and another 4 in the other group (Group B), but this time are suspected to have the odd ball among them and to be lighter.
Place 3 from (A) + 2 from (B) on side (1), and place the normal 4 balls + 1 from (A) on side (2).
If they balance, then one of the two remaining balls from (B) is the odd ball and it should be lighter, so we place them on the scale and the lighter is the odd one.
If side (1) goes down, that means one of the 3 balls of (A) is the odd and heavier, so we place one of them on a side and another on the other side, if they balance then the third one is the odd, if they don't, then the heavier is the odd.
If side (2) goes down, that means either one of the 2 balls of (B) on side (1) is the odd and lighter, or the ball of (A) on side (2) is the heavier, we place the two balls of (B) on the scale, if they balance, then the ball of (A) on side (2) is the odd and heavier, if they don't, then the lighter one is the odd.


Take care,

:rolleyes:

[© MATCHLESS]

Yours is more complicated

and...

What I have said was quit true



take care

:)