Question

ABCD is a parallelogram with $\angle$ABC=${90}^{\circ }$, then number of right angles in the parallelogram excluding $\angle$ABC is/are ____?

• A. 2
• B. 3
• C. 4
• D. cannot be found

Answer 1

The correct option is B

3

ABCD is the given parallelogram.

In a parallelogram, opposite internal angles are equal.

So $\angle$ABC= $\angle$ADC=${90}^{\circ }$

Also, $\angle$BAD= $\angle$BCD

In a quadrilateral, sum of all internal angles is ${360}^{\circ }$.

So $\angle$BAD+$\angle$BCD= ${180}^{\circ }$.

Therefore $\angle$BAD= $\angle$BCD= ${90}^{\circ }$.

So the number of internal right angles is 4 and excluding $\angle$ABC it will be 3.