A shopkeeper decides to raise the marked price of an article by 40%. How much percentage discount should he allow to be able to sell the article at the original marked price?

Correct option is D

Given:
Raise the MP = 40%
Formula Used:
​$$\text{Discount\%} = \frac{\text{Marked Price - Selling Price}}{\text{Marked Price}} \times 100$$​​
Solution:
Let the original price be 100
As per the question
Marked price = 100 ×$$\frac{140}{100}$$​=140
As given in the question that CP = SP
Discount% = $$\frac{140-100}{140}$$​ ×100
​$$= \frac{40}{140}×100\\= \frac{2}{7}×100\\= 28\frac{4}{7}\%\\$$​​
Alternate Method:
Let original price be 100
Marked price = 140
100 : 140
5 : 7
Discount% =$$\frac{(7-5)}{7} ×100 = \frac{2}{7}×100 = 28\frac{4}{7}\%$$​​