The marked price of an article is ₹3500 and rate of GST is 12 percent. A shopkeeper allows a discount of 20 percent and still makes a profit of 10 percent. Find the original cost price of the article and the selling price including GST.

Answer

Marked price = rs. 3500

GST % =12 %

so, SP = 3500 + 12% of 3500

or, SP = 3500 + 0.12 ×3500 = rs. 3920

After discount the new SP 

= 3920 - 20% of 3920

= 3920 - 0.20×3920

= rs. 3136 (1)                                               profit% = 10 % ; SP = rs. 3136 

Let CP = X

so, SP = CP + 10% of CP 

or, 3136 = X + 0.10 X

or, 3136 = 1.10 X

or, X = 3136/1.10 

original CP = 2850.909.                            { you can also  use a formula,

Cp=(SP*100)/100+profit%}