A man sold two flats for Rs. 4.15 lakhs each. On one he gained 2% and on the other he lost 2%. What percent is the effect of the sale on the whole ?

In this type cases we always have loss only.

Loss% =  $\frac{Common Gain or Loss}{10}2$=  $\frac{2}{10}2$= 1/25 = 0.04 %