Dimensiunile initiale, sunt L=1260dm si l=2400cm=240dm;
daca lungimea creste cu x decimetri, vom avea:
75dam=2*)1260+x+240)dm
inseamna ca:
2*1500dm+2x=7500dm
2x=4500dm-3000dm=4500dm
x=4500:2=2250dm
=> A₁=1260dm*240dm=302400dm² ;
Aria actuala este:
A₂=(1260+2250)*240=3510*240=842400dm²
A₂ - A₁ = 840000dm² ;