Average Practice Test 1

Question : 28 of 40

Marks: +1, -0

In an examination, the average mark obtained by students who passed was x%, while the average of those who failed was y%. The average mark of all the students who took the examination was z%. Find in terms of x, y and z the percentage of student, who failed examination.

${z-x}/{y-x}$
${x-z}/{y-x}$
${y-x}/{z-y}$
${y-z}/{x-z}$

Validate

Solution:

Let the number of students passed is greater than the number of students failed.
By using allegation approach,

So, students passed = z - y
Students failed = x - z
Total students = (z - y) + (x - y) = x - y
Ratio of students failed to total students

={x-z}/{x-y}

={-(z-x)}/{-(y-x)}={z-x}/{y-x}

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