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# Classifying quadrilaterals

Sal classifies quadrilaterals by their properties (such as parallel sides). Created by Sal Khan.

Video transcript

A parallelogram is a blank with
two sets of parallel lines. So let's see what
the options are. So one option is
a quadrilateral. And a parallelogram is
definitely a quadrilateral. A quadrilateral is
a four-sided figure, and it is definitely
a four-sided figure. A parallelogram is
not always a rhombus. A rhombus is a special case of a
parallelogram where not only do you have to sets
of parallel lines as your sides, two
sets of parallel sides, but all of the sides are the
same length in a rhombus. And a square is a special
case of a rhombus where all of the angles
are 90 degrees. So here, all we can say
is that a parallelogram is a quadrilateral. And so let's check our answer. And it's always a good
idea to look at hints. And so it'll kind of say the
same thing that we just said, but it would say it for
the particular problem that you're actually looking at. Let's do a few more of these. Suzanne is on an expedition
to save the universe. Sounds like a reasonable
expedition to go on. For her final challenge,
she has to play a game called Find
the Rhombuses. A wizard tells her that she
has a square, a quadrilateral, and a parallelogram,
and she must identify which of the
shapes are also rhombuses. Which of these shapes should
she pick to save the universe? So a square is a special
case of a rhombus. Just to remind ourselves, a
rhombus, the opposite sides are parallel to each other. You have two sets
of parallel sides. A square has two sets
of parallel sides, and it has the extra condition
that all of the angles are right angles. So a square is definitely
going to be a rhombus. Now, all rhombuses
have four sides. So all rhombuses
are quadrilaterals. But not all quadrilaterals
are rhombuses. You could have a quadrilateral
where none of the sides are parallel to each other. So we won't click this one. Once again, a parallelogram. So all rhombuses
are parallelograms. They have two sets
of parallel sides, two sets of parallel
line segments representing their sides. But all parallelograms
are not rhombuses. So I would say that if
someone gives you square, you can say, look, a square is
always going to be a rhombus. A quadrilateral isn't always
going to be a rhombus, nor is a parallelogram
always going to be a rhombus. We got it right.