Question

a man sold two paintings at rupee 924 each on one he gain 20% and on the other he lost 20% How much does he gain or loss in the whole transaction

Answer 1

In the case where loss and gain percentage is common on same selling price, always a loss incurs in total deal. And this can be calculated by a short-cut:
Loss on total deal,
= (Common loss or gain percentage /10)2 = (20/10)2
= 4%

Alternatively, It can be also calculated through Graphic Change Method: This can be given by,
100==20% gain ==>120==20% loss==>96.
Loss = 4% (As 100 became 96).