Question

A stationer buys pens at 5 for Rs.28 and sells them at a profit of 25%. How much should a customer pay; if he buys (i) only one pen ? (ii) three pens ?

Answer 1

For Stationer :
C.P. of 5 pens = Rs. 28
C.P. of 1 pen = $\frac{28}{5}$ Rs. = Rs. 5.60
Profit = 25%
$\therefore$ S.P. of 1 pen
= $\frac{(100+Profit}{100}\times$ C.P. of 1 pen
= $\left(\frac{100+25}{100}\right)\times Rs.5.60=Rs.\frac{125}{100}\times 5.60$
= Rs. $\frac{125\times 5.60}{100}=Rs.5\times 1.4=Rs.7$
S.P. of 3 pens = 3 $\times$ 7 = Rs. 21
$\therefore$ Customer pays for
(i) only one pen = Rs. 7
(ii) Three pens = Rs. 21