Question

din 900 de kg de fier se extrage 150 kg fier pur . aflati cantitatea de minereu de fier  din care se extrage 500 kg de fier

Answer 1

900...................150
500.....................x
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$\frac{900}{500}$=$\frac{150}{x}$
⇔x=$\frac{150*500}{900}$=$\frac{150*5}{9}$=$\frac{750}{9} =83,(3)$

Answer 2

aplici regula de 3 simple:
900kg.........150kg
500kg.........x kg

500*150=75000
75000/900=83 ,33 kg minereu