Let number 12 balls as A1 A2 A3 A4; B1 B2 B3 B4; C1 C2 C3 C4;

First measure: A1 A2 A3 A4 and B1 B2 B3 B4. Second and third measure: If As=Bs then compare A1 A2 A3 and C1 C2 C3 If A1+A2+A3=C1+C2+C3 then compare A1 and C4----> solved. If A1+A2+A3>C1+C2+C3 then compare C1 and C2---> solved If A1+A2+A3<C1+C2+c3 then compare C1 and C2 ---> solved

If As>Bs then compare A1+B2+B3+B4 and B1+C2+C3+C4 If A1+B2+B3+B4=B1+C2+C3+C4 then compare A2 and A3---> solved If A1+B2+B3+B4>B1+C2+C3+C4 then compare A1 and A2---> solved If A1+B2+B3+B4<B1+C2+C3+C4 then compare B2 and B3---->solved

IF As<Bs, we can get the answer similarly.

Ziqing Pan zpan@aol.com