When the price of an article was increased by 5% its sale reduced by 10%. What was net effect on the revenue?

5.5% decrease 

Revenue = Price x Sale

When price increase by 5% and sale reduces by 10%

Change in revenue = $\frac{105}{100}$ x $\frac{90}{100}$ original revenue

                            = $\frac{945}{1000}$

                            = 5.5% decrease