Assume all marbles are from 10g and the heavier one is 11g Take 1 marble from bag1 ,2 from bag2, 3 from bag3, 4 from bag4, 5 from bag5, 6 from bag6, 7 from bag7, 8 from bag8, 9 from bag9,10 from bag 10..and weigh them together Let it be W. So if bag5 contains the heavy marbles The total weight (W) will be 10+20+30+40+55+60+70+80+90+100 = 555. where as if all were of 10g it should have been 550. meaning the bag which is heavy will always be MeasuredWeight - 550 Mathematically if bag X is the one which is heavy, X can be found using one weighing of sample (W) - (N(N+1)/2)

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