I need some help in Physics.?

Question

A 100 gram meter stick is hung by a string from its center. Masses of 40 grams, 80 grams, and 20 grams are suspended from the stick at the 10 cm, 40 cm, and 70 cm marks respectively. Where should a 50 gram mass be placed to balance the stick?

Answer 1

summing torques at the center point

40*40+80*10-20*20-50*d=0

solve for d
d=40

Location is 50+d=90 cm

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