the marked price of a book is 20 % more than the cost price. after the book is sold, the vendor realizes that he had wrongly raised the cost price by a margin of 25 %. if the marked price of the book is rs. 30, what is the original cost price of the book?	Choose the correct option
A) rs . 30	B) rs . 25	C) rs . 45	D) rs . 20	E) rs . 10
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">30 / (6/5)</gadget>
<output>25</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + (1/4)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">25 / (5/4)</gadget>
<output>20</output>

<result>D</result>
the marked price of a book is 20 % more than the cost price. after the book is sold, the vendor realizes that he had wrongly raised the cost price by a margin of 25 %. if the marked price of the book is rs. 30, what is the original cost price of the book?
divide(divide(30, add(const_1, divide(20, const_100))), add(const_1, divide(25, const_100)))
let the incorrect cost price be c 1 and let the original cost price be c 2 . marked price of book is rs . 30 . it is 20 % more than c 1 . therefore , ( 120 / 100 ) x c 1 = 30 or c 1 = 25 . c 1 is more than c 2 margin of 25 % . or c 1 = ( 125 / 100 ) c 2 therefore , c 2 = ( 100 / 125 ) x 25 = rs 20 answer : d