The average price of 10 books is Rs.12 while the average price of 8 of these books is Rs.11.75. Of the remaining two books, if the price of one book is 60% more than the price of the other, what is the price of each of these two books?

Explanation:-

$$\eqalign{ & {\text{Total}}\,{\text{cost}}\,{\text{of}}\,10\,{\text{books}} = Rs.\,120 \cr & {\text{Total}}\,{\text{cost}}\,{\text{of}}\,8\,{\text{books}} = Rs.\,94 \cr & \Rightarrow {\text{The}}\,{\text{cost}}\,{\text{of}}\,2\,{\text{books}} = Rs.\,26 \cr & {\text{Let}}\,{\text{the}}\,{\text{price}}\,{\text{of}}\,{\text{each}}\,{\text{book}}\,{\text{be}}\,x\,{\text{and}}\,y. \cr & \Rightarrow x + y = 26\, - - - - - - \left( 1 \right) \cr & {\text{Given}}\,{\text{that}}\,{\text{the}}\,{\text{price}}\,{\text{of}}\,{\text{1}}\,{\text{book}}\,{\text{is}}\,60\% \,{\text{more}}\,{\text{than}}\,{\text{the}}\,{\text{other}}\,{\text{price}} \cr & \left( {\frac{{160}}{{100}}} \right)y + y = 26 \cr & y\left( {\frac{{160}}{{100}} + 1} \right) = 26 \cr & y\left( {\frac{{160 + 100}}{{100}}} \right) = 26 \cr & y = \frac{{\left( {26 \times 100} \right)}}{{260}} \cr & y = 10 \cr & \cr & {\text{Substituting}}\,Y = 10\,{\text{in}}\,\,\,\left( 1 \right)\,{\text{we}}\,{\text{get}}, \cr & x + 10 = 26 \cr & x = 16 \cr}$$