Question

Un dreptunghi are dimensiunile direct proportionale cu nr 5 si 7,iar perimetrul acestuia este egal cu 168 cm. Aflati aria dreptunghiului.

Answer 1

Fie x si y-dimensiunile dreptunghiului.
{x, y}---->d.p{5,7}=>x/5=y/7=k
x/5=k=>x=5k
y/7=k=>y=7k
P=2(L+l)
P=2(x+y)
P=2(5k+7k)=168 cm
2*12k=168 cm
24k=168 cm
k=168 cm/24
k=7 cm=>x=35 cm si y=49 cm
A=L*l=49 cm*35 cm=1715 cm^2
sau 


{x, y}--->d.p {5,7}=>x/5=y/7=>x=5y/7
P=2(L+l)
P=2(x+y)
2(5y/7+y)=168 cm
2(5y/7+7y/7)=168 cm
2*12y/7=168 cm
24y/7=168 cm=>y=168 cm*7/24=49 cm
=>x=5*49/7=35 cm
A=L*l=49 cm*35 cm=1715 cm^2