MAT Exam 2021 Paper

Concept:Percentages are applied sequentially to find the pure iron obtained from the mined ore.Explanation:Let the total quantity of hematite mined be $x$ kg.$20\%$ of the ore is wasted, so the remaining ore is $80\%$ of $x$.Only $25\%$ of this remaining ore is pure iron.Therefore, pure iron obtained $= 25\% \times 80\% \times x$.This gives $= \frac{25}{100} \times \frac{80}{100} \times x = \frac{1}{5}x$ kg.Given that pure iron obtained is $80000$ kg, we have:$\frac{1}{5}x = 80000$$x = 80000 \times 5 = 400000$ kg.Answer:The quantity of hematite mined is $400000$ kg, which is option A.