If each of the two dimensions of a rectangle is increased by 100%, by what percentage is the area increased?
If the original length is x and the original width is y, then the area will be: A = xy.
If you increase the length by 100%, you are doubling the length to 2x.
If you increase the width by 100%, you are doubling the width to 2y.
The new area will be: A = 2x·2y = 4xy.
The increase in area will be: 4xy - xy = 3xy.
The percentage increase will be: 3xy / xy = 3, or 300%.