If a boy sells a book for Rs. 450 he gets a loss of 10 %, then find cost price. To gain 10 %, what should be the selling price?	Choose the correct choice from the following options.
A) 400, 500  B) 550, 600  C) 500, 550  D) 475, 525  E) 520, 450
1) Find cost price   Let C.P. of book = x and S.P. = Rs. 450   S.P. of book = C.P. – (10% of C.P.)   S.P. = x – (0.10x)   450 = 0.9 x   x i.e cost price = Rs. 500   2) Find Selling Price to gain 10 %.   Now, we are asked to find selling price to gain 10% profit.   Hint:   Selling Price =	(100 + Gain%)	/100*C.P.   Selling Price =	(100 + 10)/100*500   Selling Price =	(110/100)*500   Therefore, selling Price = Rs. 550   ANSWER IS 500, 550
<result>C</result>
If a boy sells a book for Rs. 450 he gets a loss of 10 %, then find cost price. To gain 10 %, what should be the selling price?