To solve this, first solve for a length (L) that will make the perimeter 90cm exactly.
Perimeter of a rectangle is:
P = 2L + 2W
Where P is the perimeter, L is the length, and W is the width.
Using this we can solve for L by filling in P and W
90 = 2L + (2 * 20)
90 = 2L + 40
50 = 2L
25 = L
Now we know that when the length is 25cm, the perimeter is 90cm. Since the problem states the rectangle must have a perimeter greater than 90cm, we can simply deduce that the length must be greater than 25cm. So...
L > 25cm
Perimeter of a rectangle is:
P = 2L + 2W
Where P is the perimeter, L is the length, and W is the width.
Using this we can solve for L by filling in P and W
90 = 2L + (2 * 20)
90 = 2L + 40
50 = 2L
25 = L
Now we know that when the length is 25cm, the perimeter is 90cm. Since the problem states the rectangle must have a perimeter greater than 90cm, we can simply deduce that the length must be greater than 25cm. So...
L > 25cm
