Question

In a traingle ABC

Given : $\angle A=9x-{15}^o;\angle B=4xand\angle C=3x+{15}^o$. Calculate $\angle B$

• A. ${40}^o$
• B. ${45}^o$
• C. ${60}^o$
• D. none of the above

Answer 1

Answer: (B)

${45}^o$

Using angle sum property of triangle.

$\angle A+\angle B+\angle C={180}^{\circ }\Rightarrow 9x-{15}^{\circ }+4x+3x+{15}^{\circ }={180}^{\circ }\Rightarrow 16x={180}^{\circ }\Rightarrow x=\frac{{180}^{\circ }}{16}={11.25}^{\circ }\angle B=4x=4\times {11.25}^{\circ }={45}^{\circ }$