Question

The angles of a quadrilateral are in $A.P$. whose common difference is ${10}^0$, then the first angle in $A.P$. is

Answer 1

Let the angles be a, $a+d,a+2d,a+3d$

$\Rightarrow a+a+d+a+2d+a+3d={360}^o$

$\Rightarrow 4a+6d={360}^o$ $(d=10)$

$\Rightarrow 4a=360-60$

$\Rightarrow a=\frac{300}{4}={75}^o$.