CTET 2 Math and Science Dec 2019 Paper

Let the angles of a quadrilateral are 3x, 5x, 7x and 9x
∵ Sum of the angles of any quadrilateral = 360°
∴ 3x + 5x + 7x + 9x = 360°
⇒ 24x = 360°
$\Rightarrow \mathit{x}=\frac{360°}{24}=15°$
Least angle = 3 × 15 = 45°
Greatest angle = 9 × 15 = 135°
Difference = 135° – 45° = 90°.