Step-by-step explanation:
in a rect.
b:l=1:4
let,
"x" & "4x"
perimeter=20cm
thus,
2(l+b)=20
x+4x=20/2
5x=10
x=10/5
x=2
also
4x=4×2
=8
also ,area=
l×b
=8×2
=16
thus,area=16
