Question

If in a quadrilateral ABCD, $\angle A={120}^o,\angle B={60}^o,\angle C={100}^o$ then $\angle D=$ ...............

• A. 80${}^o$
• B. 90${}^o$
• C. 180${}^o$
• D. 360${}^o$

Answer 1

The correct option is A 80${}^o$

$\angle A+\angle B+\angle C+\angle D={360}^o$
${120}^o+{60}^o+{110}^o+\angle D={360}^o$
${280}^o+\angle D={360}^o$
$\angle D={360}^o-{280}^o={80}^o$