A shopkeeper earns a profit of 21% after selling a book at 21% discount on the printed price. The ratio of the cost price and selling price of the book is :
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Correct answer: D
Explanation
The correct answer is option 4 i.e. 100 : 121
Let the cost price of the book be 100x
After applying the discount still shopkeeper earns a profit of 21%
Selling price = 100x × 1.21
⇒ 121x
⇒ 100x : 121x = 100 : 121