One side of a rectangle is three times the other. If the perimeter increases by 2%, what is the percentage increase in area?
I've started with these few lines:
Perimeter, P = 2x + 2x + x + x = 8x
Area, 3x^2 = 3(p^2)/64
delta P= 2%
delta A = dA/dP . delta P
delta A = 3/64 (2p). 2%
The answer is 4% but it doesn't look like delta A will be 4%!
Any clues where I went wrong? Thanks.