MCQ
While preparing the progress reports of the students, the class teacher found that $70\%$ of the students passed in Hindi, $80\%$ passed in English and only $65\%$ passed in both the subjects. Find out the percentage of students who failed in both the subjects.
  • $15\%$
  • B
    $20\%$
  • C
    $30\%$
  • D
    $35\%$

Answer

Correct option: A.
$15\%$
The sets $E$ and $H$ represent the students failing in the respective subjects.
$\ce{n(H ∪ E)} = 1− 0.65 = 0.35$
By set theory
$\ce{n(H ∩ E) = n(H) + n(E) − n(N ∪ E)}$
$= 0.3 + 0.2 − 0.35 = 0.15$
Hence $15\%$ of students failed in both subjects.

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