At what percent above the cost price must a shopkeeper mark his goods so that he gains 20% even after giving a discount of 10% on the marked price ?

A) 25%

B) 30%

C) $33\frac{1}{3}$%

D) $37\frac{1}{2}$%

E) 40%


Option C


Let C.P = Rs. 100. Then S.P = Rs. 120.

Let marked price be Rs. $x$. Then, 90% of $x=120$ $\Rightarrow$ $x$ $=\left(\frac{120 \times 100}{90}\right)$

$\therefore$ Marked price $=33\frac{1}{3}$% above C.P