A shopkeeper buys 100 pens for 200 and sells20 of them at a gain of 10

1.	A shopkeeper buys 100 pens for 200 and sells20 of them at a gain of 10%. At what gain per centmust he sell the remainder so as to gain 20% in all
Answer» CP of 100 pens= 200CP of 1 pen= 200/100CP of 20=200/100 ×20=Rs.40 g% of 20 pens= 10% SP of 20 pens= 100+gain/100 × CP=100+10/100 × 40=44 g% of whole lot, i.e. 100 pens= 20%SP of 100 pens= 100+20/100 ×200= 240 CP of 80 pens= 200-40= 160SP of 80 pens= 240-44= 196Gain on 80 pens= 196-160= 36G%= 36/160 ×100= 22.5%

A shopkeeper buys 100 pens for 200 and sells20 of them at a gain of 10%. At what gain per centmust he sell the remainder so as to gain 20% in all

Answer»

CP of 100 pens= 200CP of 1 pen= 200/100CP of 20=200/100 ×20=Rs.40

g% of 20 pens= 10%

SP of 20 pens= 100+gain/100 × CP=100+10/100 × 40=44

g% of whole lot, i.e. 100 pens= 20%SP of 100 pens= 100+20/100 ×200= 240

CP of 80 pens= 200-40= 160SP of 80 pens= 240-44= 196Gain on 80 pens= 196-160= 36G%= 36/160 ×100= 22.5%