Heavy Marble

Question

You have 8 marbles. They all look identical. However, one marble weighs more. A balance scale is available, but you you can just use it 2 times. How can you find the heavy marble?

Answer 1

I figured this one out. First divide into 3 and 3 with 2 extra marbles on the side.

xxx xxx xx

Weigh the 2 sets of 3

xxx ---- xxx

If they weigh the same, just weight the extra 2 to find the heavy marble.

If one is heavier, remove the lighter set and select 2 from the heavier set.

x ---x  x

If they weigh the same, the heavy marble was the outside one. If one is heavier you also know the heavy marble.

Answer 2

 

Make 2 groups of 4 marbles and weigh. The group that weighs more, split it into another 2 groups of 2 marbles and weigh. The group that weighs the most has the heavy marble, and to find which one, put one in either palm and feel which one is heavier...?

I don't really know...

-CraftyGirlJuJu

 

P.S. If you're wondering why there are two answers the same, I forgot to login, so..

Comments

Sometimes I do that too. After you log in, there's a button next to "flag"(I think), called "I wrote this". Then you can just click on that so that you don't have to write your answer again.
Hopefully this helps!

Answer 3

Make 2 groups of 4 marbles and weigh. The group that weighs more, split it into another 2 groups of 2 marbles and weigh. The group that weighs the most has the heavy marble, and to find which one, put one in either palm and feel which one is heavier...?

I don't really know...

-CraftyGirlJuJu