A's marks in Biology are 20 less than 25\% of the total marks obtained by him in Biology, Maths and Drawing. If his marks in Drawing be 50, what are his marks in Maths?
(a)40
(b)45
(c)50
(d)Cannot be determined
Answer
Answer (as printed): D
Explanation
Let $\mathrm{B}+\mathrm{M}+\mathrm{D}=x$. Then, $\mathrm{B}=25 \%$ of $x-20$ $$\begin{aligned} & =\left(\frac{25}{100} x-20\right)=\left(\frac{x}{4}-20\right) \text { and } \mathrm{D}=50 . \\ & \therefore \frac{x}{4}-20+\mathrm{M}+50=x \text { or } \mathrm{M}=\left(\frac{3 x}{4}-30\right) . \end{aligned}$$ So, marks in Maths cannot be determined.
Explanation as extracted from the printed page; notation may be imperfect.