### A shopkeeper marks his goods 30% above his cost price but allows a discount of 10% at the time of sale. His gain is:

A. 21% B. 20% C. 18% D. 17% Answer: Option D
Let the cost price be Rs. 100 then the mark up price which is 30% above the cost price, Mark price = (100 + 30% of 100) = Rs. 130 Shopkeeper gives a discount of 10% on mark up price, then the Selling Price = (130 – 10% of 130) = Rs. 117 Gain = 117 – 100 = Rs. 17 $\text{%gain }=\frac{17\times100}{100}=17\%$ Short Cut method: 100(CP) == 30%↑ ⇒ 130(MP) == 10%↓ ⇒ 117(SP) Gain = 17%