Previously, the manufacturing cost of a product was thrice the cost of raw material. Now the cost of raw material increases in the ratio 5 : 12 and manufacturing cost increases in the ratio of 3 : 5. The previous cost of the product was Rs. 8. What should be the present selling price so that 25% profit can be made?

Explanation:-

Original C.P. of the product = Rs. 8.
Original manufacturing cost $$\eqalign{ & = {\text{Rs}}.\left( {\frac{3}{4} \times 8} \right) \cr & = {\text{Rs}}{\text{. }}6 \cr}$$ Original cost of raw material $$\eqalign{ & = {\text{Rs}}.\left( {8 - 6} \right) \cr & = {\text{Rs}}{\text{. }}2 \cr}$$ New manufacturing cost $$\eqalign{ & = {\text{Rs}}.\left( {\frac{5}{3} \times 6} \right) \cr & = {\text{Rs}}{\text{. }}10 \cr}$$ New cost of raw material $$\eqalign{ & = {\text{Rs}}.\left( {\frac{{12}}{5} \times 2} \right) \cr & = {\text{Rs}}{\text{. }}\frac{{24}}{5}. \cr}$$ New S.P. of the product $$\eqalign{ & = {\text{Rs}}.\left( {10 + \frac{{24}}{5}} \right) \cr & = {\text{Rs}}{\text{. }}\frac{{74}}{5}. \cr}$$ $$\eqalign{ & \therefore {\text{Desired S}}{\text{.P}}{\text{.}} \cr & = 125\% {\text{ of Rs}}.\frac{{74}}{5} \cr & = {\text{Rs}}{\text{.}}\left( {\frac{{125}}{{100}} \times \frac{{74}}{5}} \right) \cr & = {\text{Rs}}.18.50. \cr}$$