Question

Total cost of $15$ erasers and $25$ pencils is Rs. $185$ and the total cost of $9$ erasers and $x$ pencils is Rs. $106$. Which of the following cannot be the value of $x$?

• A. $12$
• B. $10$
• C. $13$
• D. $15$

Answer 1

The correct option is D $15$

Let cost of eraser be $e$ and cost of pencil be $p$
As per given statements, we have
$15e+25p=185$
$=>3e+5p=37$
$=>3e=37-5p$ --- $\left(1\right)$
Also, $9e+xp=106$ --- $\left(2\right)$
From eqns $\left(1\right),\left(2\right)$, we have
$3(37-5p)+xp=106$
$=>111-15p+xp=106$
$=>(15-x)p=5$ --- $\left(3\right)$
From , we understand that $x\ne 15$ as LHS of eqn $3$ will be zero but RHS $=5$.