By selling 90 ball pens for Rs. 160, a person loses 20% . How many ball pens should be sold for Rs. 96 so as to have a profit of 20% ?

Solution (By Examveda Team)

$$\eqalign{ & {\text{S}}{\text{.P}}{\text{. of 90 ball pens}} \cr & = {\text{Rs}}{\text{. 160, loss}} = 20\% \cr & {\text{C}}{\text{.P}}{\text{.of 90 ball pens}} \cr & = {\text{Rs}}.\left( {\frac{{100}}{{80}} \times 160} \right) \cr & = {\text{Rs}}{\text{. }}200 \cr} $$
∴ Desired S.P. of 90 ball pens
$$\eqalign{ & = {\text{Rs}}.\left( {\frac{{120}}{{100}} \times 200} \right) \cr & = {\text{Rs}}{\text{. }}240 \cr} $$
For Rs. 240, ball pens sold = 90
For Rs. 96, ball pens sold
$$\eqalign{ & = \left( {\frac{{90}}{{240}} \times 96} \right) \cr & = 36 \cr} $$