Question

URGENT 30 puncte!.Calculati aria dreptunghiul stiind ca perimetrul este 126cm si latia este 40% din lungime

Answer 1

$P=2l+2L \\ P=126 \\\\ l=40\% \ din \ L \\\\ l= \frac{40}{100}*L = \frac{10}{25}*L = \frac{2}{5}*L\to\boxed{\frac{2L}{5}} \\\\ 2* \frac{2L}{5}+2L=126 \\\\\frac{4L}{5}+2L^{(5}=126^{(5} \\\\ 4L+10L=126*5 \\\\ 14L=126*5 \\\\ L= \frac{126*5}{14} \\\\ L=9*5 \\\\ \boxed{\boxed{L=45}} \\\\ l= \frac{2*45}{5} \\\\ l= 2*9 \\\\ \boxed{\boxed{l=18}} \\\\\\ A=L*l \\\\ A= 18*45 \\\\ \boxed{\boxed{A=810}}$