Answer:
width=9 cm
length =36cm
Explanation:
let us suppose width of rectangle be x
then,length of rectangle =4x
given, perimeter of rectangle =90cm
we know that,
perimeter of rectangle=2(length + width)
90cm=2(4x+x)
or,90/2cm=5x
or,45cm=5x
or,(45/5)cm=x
or,x=9cm..
therefore ,width(x)=9 cm
and length (4x)=4*9=36cm