ABCD is a parallelogram. What information would NOT allow you to conclude that ABCD is a rectangle?

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Question

ABCD is a parallelogram. What information would NOT allow you to conclude that ABCD is a rectangle?

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anonymous · Answer

it would be the angle DAB=90 degrees.

anonymous · Answer

@MathGuyThatWantsHelp But I thought rectangles have 4 right angles? I'm trying to find the answer on how not to conclude that its a rectangle..

anonymous · Answer

its either the first answer or the fourth answer because it only has 3 points not telling us if there is any more than just 3

anonymous · Answer

@MathGuyThatWantsHelp  I don't understand what you mean.....I thought at first it was the third because rectangles don't have 4 equal sides?

anonymous · Answer

***I thought it was the third answer

anonymous · Answer

the measurements can be different with the third answer it doesn't say that all the sides are equal. 
I read it carefully and the best answer i can think of is the first one.

anonymous · Answer

Okay thank you! @MathGuyThatWantsHelp

mathstudent55 · Answer

Answer D is not it. A parallelogram has two pairs of congruent opposite angles. If only one angle is known to be a right angle, then the angle opposite that angle is also a right angle. Those two opposite angles add up to 180 degrees. There are 180 degrees left for the other two angle, but since they are congruent, they measure 90 degrees each, so all angles are right angles and it's a rectangle.

mathstudent55 · Answer

Answer B is also not it. If a parallelogram has congruent diagonals, then it is a rectangle.

mathstudent55 · Answer

Answer A is also not it. The diagonals of a parallelogram bisect each other. The diagonals of a rectangle are congruent. If those two half diagonals are congruent, then the diagonals are congruent and this parallelogram is a rectangle.

mathstudent55 · Answer

That leaves only choice C.
If each pair of adjacent sides of a parallelogram is congruent, then that makes the parallelogram a rhombus, but it does not make it a rectangle.

anonymous · Answer

Thank you so much! I understand it now!! Thank you @mathstudent55

anonymous · Answer

@mathstudent55 could you help me with another question please?

mathstudent55 · Answer

You're welcome.