The length of a triangle is two times its width.
The perimeter of the rectangle is 90 cm.
Calculate the length, and the width of the rectangle.
Let the width of the triangle be x.
Then the length of the triangle is 2x.
The perimeter of the rectangle is 90 cm, which means:
perimeter = 2(length + width)
90 = 2(2x + x)
90 = 2(3x)
90 = 6x
x = 15
So, the width of the rectangle is 15 cm, and the length is 2(15) = 30 cm.