IXL | Find missing angles in quadrilaterals II

One angle of a parallelogram measures 50°. What are the measures of the other three angles in the parallelogram?

°, °, and °

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question

One angle of a parallelogram measures 20°. What are the measures of the other three angles in the parallelogram?

°, °, and °

key idea

Opposite angles of a parallelogram are congruent.

The measures of the angles of a parallelogram add up to 360°.

solution

One of the missing angles is opposite the 20° angle. Since opposite angles are congruent, this missing angle is 20°.

Find the other two missing angles. Set the sum of the angle measures equal to 360° and solve.

20° + 20° + n + n

360°

Add

40° + 2n

360°

Add

Subtract 40° from both sides

360° − 40°

Subtract 40° from both sides

Simplify

320°

Simplify

Divide both sides by 2

160°

Divide both sides by 2

Two of the missing angles are 160°.

So, the missing angles are 20°, 160°, and 160°.

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