RRB NTPC 28 April 2016 Paper

(4) C.P. of 12 books =S.P. of 8 books
Let C.P. of 1 book = ₹ 100
C.P. of 12 books =₹ 1200 = S.P. of8 books
S.P. of 1 book = $\frac{1200}{8}$ = 150
Profit = S.P. − C.P.= 150 – 100= ₹ 50
Profit $\%=\frac{\mathit{p}\mathit{r}\mathit{o}\mathit{f}\mathit{i}\mathit{t}}{\mathit{C}\mathit{P}}\times 100$$=\frac{50}{100}\times 100=50\%$