The figure represents a mobile in balance. Not counting the weight of the horizontal bars and that of the wires, the weight of the mobile is 112 grams. How much does the star weigh?
Since the mobile is in balance, the weight that supports each arm must be the same. In this way, if we divide the weight of the mobile by two at each fork we will have the weight of each end. Thus, half will be worth 112/2 = 56. From the area where the star is, we must divide again by 2, and 56/2 = 28 (the square) comes out. Then we divide again by 2 and there is 14 (the triangle) and then we get the weight of the star by dividing again by 2, so weighs 7gr.