The average marks obtained by 180 students in an examination is 50. If the average marks of passed students is 80 and that of the failed students is 40, then what is the number of students who failed the examination?
Let number of failed students in the class be x. Then number of passed students will be (180 - x)
And total number of students = 180 x 50 = 9000
$$\therefore$$ 40x + 80(180 - x) = 9000
$$\Rightarrow$$ 5400 = 40x (or) x = 135
Hence, option B is the correct answer.
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