Question

Arithmetic mean of marks (out of $25$) scored by $10$ students was $15$. One of the student, named Karishma enquired the other $9$ students and find the deviations from her marks are noted as $-8,-6,-3,-1,0,2,3,4,6$. Find Karishmas marks

Answer 1

Let Krishna's marks be $x$ marks.

$\overline{x}=15$

$n=10$

$\sum x=x+x-8+x-6+x-3+x-1+x+x+2+x+3+x+4+x+6=10x-3$

$15=\frac{10x-3}{10}$

$150+3=10x$

$x=\frac{153}{10}=15.3$ $marks.$

$\therefore$ Krishna scored $15.3$ $marks.$