Question

By selling a book for Rs 258, a bookseller gains 20%. For how much should he sell it to gain 30%?

Answer 1

$$\begin{gathered} \mathrm{Selling}\mathrm{price}\mathrm{of}the\mathrm{book}=\mathrm{Rs}.258 \\ \mathrm{Gain}\%=20\% \\ \mathrm{Since},\mathrm{C}.\mathrm{P}=\left[\frac{100}{\left(100+\mathrm{Gain}\%\right)}\times S.P\right] \\ =\left[\frac{100}{\left(100+20\right)}\times 258\right] \\ =\frac{25800}{120} \\ =\mathrm{Rs}.215 \\ \mathrm{Let}\mathrm{the}\mathrm{bookseller}sells\mathrm{it}for\mathrm{Rs}.x \\ So,S.P=\left[\frac{\left(100+\mathrm{Gain}\%\right)}{100}\times C.P\right] \\ x=\frac{100+30}{100}\times 215 \\ =\frac{130\times 215}{100} \\ =\mathrm{Rs}.279.50 \\ \mathrm{Therefore},the\mathrm{bookseller}\mathrm{must}\mathrm{sell}thebookat\mathrm{Rs}279.50\mathrm{to}make30\%profit. \end{gathered}$$