The angles of a quadrilateral are in the ratio 3 : 5 : 7 : 9. What is the difference between the least and the greatest angles of the quadrilateral?

Sum of angles in a quadrilateral = 360°. Let angles be 3x, 5x, 7x, 9x. Then 3x+5x+7x+9x = 24x = 360°, so x = 15°. Angles are 45°, 75°, 105°, 135°. Difference between greatest and least = 135° - 45° = 90°. However, the answer is 90°? Let me recheck: 135 - 45 = 90°. The answer is option (4) 90°.