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%?
S.P of 90 ball pens =Rs.160
∴ S.P of 1 ball pen =Rs.16090=Rs.169
Loss =20%
∴ C.P of one pen =S.P×100100−loss%
=16×1009(100−20)
=Rs. 16×1009×80=Rs. 209
In second case,
Gain =20%
S.P of one pen =C.P×(100+gain%)100
=209×(100+20)100
=Rs. 209×120100=Rs. 83
In Rs. 83, ball pens will be sold = 1
∴ In Rs. 96, ball pens will be sold =1×38×96 =36