Question

Find the numerical value of (c - a) + (d - b).

• A. 80°
• B. 110°
• C. 90°
• D. 100°

Answer 1

The correct option is D

100°

$b={115}^{\circ }$ [Vertically opposite angles]
$c={140}^{\circ }$ [Vertically opposite angles]
$c=d={140}^{\circ }$ [Corresponding angles]
$a+b={180}^{\circ }$ [Co-interior angles]
$a={180}^{\circ }-b={180}^{\circ }-{115}^{\circ }={65}^{\circ }$

(c - a) + (d - b) = (140° - 65°) + (140° - 115°)
= 75° + 25°
= 100°