A towel, when bleached, was found to have lost 20% of its length and 10% of its breadth. The percentage of decrease in area is:

Let original length = x and original breadth = y.  

Decrease in area = xy -  $\frac{80}{100}x\times \frac{90}{100}y$ = (7/25)xy

Decrease % =    (7/25)xy * (1/xy) * 100 = 28%