Question:
A man sold two chairs at Rs. 1,200 each. On one he gained 20% and on the other he lost 20%. His gain or loss in the whole transaction is:

Option A):
1% loss
Option B):
2% loss
Option C):
15 gain
Option D):
4% loss

Correct Answer is Option D):
4% loss

Explanation:
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 and 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).