Clevers only ! 10 points?

you have to weigh one ring of the first jeweler, two rings of the second, three rings of the third and so on all together. so it should be (1+2+3+4+5+6+7+8+9+10)*10 = 550 grams. however, when e.g. three grams are missing, you know you weighed three rings of nine grams, so the guilty jeweler must be the third. When it's 540 grams, the guilty is 10. When it's 549 grams, the guilty is 1.