What is the % change in the area of a rectangle when its length increases by 10% and its width decreases by 10%?	Options:
A) 0 % B) 20 % increase C) 20 % decrease D) 1 % decrease E) insufficient data

Rationale: "explanatory answer whenever you encounter problems like this , use a numerical example and then proceed . for ease of computation , it is safe in most cases , to assume the length to be 100 units and the width to be 100 units . ( remember , a square is a rectangle too and the problem works the same way when you assume different values for length and width . computation becomes a bit tedious with different values for length and width ) area of a rectangle = length * width = 100 * 100 = 10,000 sq units . when the length increases by 10 % , the new length becomes 110 units . and as the width decreases by 10 % , new width becomes 90 units . therefore , new area = 110 * 90 = 9900 sq units . new area is 100 sq units lesser than the original area . % change in area = ( ( change in area ) / ( original area ) ) * 100 = ( 100 / 10,000 ) * 100 = 1 % decrease in area the correct choice is ( d )"
Answer: D