This ruler is three times as long as the green one.
=This ruler is twice longer than the green one.
=This ruler is three times the length of the green one.
=The length of this ruler is three times that of the green one.
This ruler is three times as long as the green one.
=This ruler is twice longer than the green one.
=This ruler is three times the length of the green one.
=The length of this ruler is three times that of the green one.