A shopkeeper marks his goods at 30% above the cost price

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

Let the CP of the article be 100.
According to the question,
The marked price = ₹ 130
Discount = 10%

∴ SP = 90% of 130 =	130 × 90	= ₹ 117
	100

∴ Gain = 117 – 100 = ₹ 17
∴ Gain percent = 17% since the CP = ₹ 100
2nd method to solve this question.
Here, r = 30%, r₁ = 10%

gain % =	r × (100 − r₁)	− r₁
	100

gain % =	30 × (100 − 10)	− 10
	100

gain % =	30 × 90	− 10 = 17 %
	100