A bookseller sold a book for RS 40.00 to make a profit of 15%.in order to earn a profit of 20%. he should have sold it for?

A) 41.74

B) 43.75

C) 42.25

D) 40.60

Given Formula

SP = Sale price

CP = Cost price 

SP = [(100 + Gain%) / 100] x CP

40 = [ ( 100+15 ) /100 ] xCP

⇒ CP = 34.78

To earn 20% profit, use 

SP = [(100 + Gain%) / 100] x CP

SP = [ (100 +20 )/100] x34.78

by solving this 

SP = 41.74