GATE 2021 ES – Question 13
Powdered-coal samples have(mass kg, carbon wt%):(2,88),(1,90),(2,80),(1,90). Find carbon weight percentage of the completely mixed sample.
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Correct answer: (B) 86%
Explanation
Total carbon=2(.88)+1(.90)+2(.80)+1(.90)=5.16 kg. Total mixture=6 kg. Carbon fraction=5.16/6=.86,or **86%,B**. Equal-weight averaging of the four percentages would ignore the unequal sample masses.