In an examination,the average marks obtained by students who passed was x%,while the average of those who failed was y%. The average marks of student taking the exam was z%. Find in terms of x, y, & z the percentage of students taking the exam who failed.

A. (z - x) / (y - x)

B. (x - z) / (y - z)

C. (y - x) / (z - y)

D. (y - z) / (x - z)

E. None of these

Solution(By Examveda Team)

Let pass = b , fail=c and total a.
b*x+c*y = a*z  ------------------------------ (1)
a = b+c
ax = bx+cx  --------------------------------------- (2)
from (1)-(2)
We get c(y-x) = a(z-x)
c/a = (z-x)/(y-x)