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### Course: Geometry (all content)>Unit 7

Lesson 7: Area of trapezoids & composite figures

# Area of kites

To find the area of a kite, you need to know the lengths of the kite's two diagonals (the lines that cross through the middle of the kite). Multiply the lengths of the two diagonals together, and then divide by 2. This will give you the area of the kite. Created by Sal Khan.

## Want to join the conversation?

• at around , sal says 56cm squared but puts the exponent 3 [A.K.A. cubed] when he should have put 2 [A.K.A. squared.]
• why do we need to know this?
• I'll give you the short term answer and the long term answer.

Short term: So we can graduate school and get a good job. We need to know math in every grade, even in college.

Long term: Throughout our life, we will need to use math in many things. Say you build a mansion with the money that you made before retiring, and you need a kite shaped pool with a volume of 3000 cubic yards of water. Would you be willing to fork over more money to the builders to calculate something you could just do yourself?

Another example would be if you were hosting a large party, and you have a kite-shaped table for all of the food. If you put too much food on the table, it will spill over. So, you need to accurately calculate how much food you will be able to fit on the table before it overflows.

Hope this helps!
• Isn't a Kite and a Rhombus the exact same thing?
• A kite is a quadrilateral with two pairs of congruent sides that are adjacent to one another. They look like two isosceles triangles with congruent bases that have been placed base-to-base and are pointing opposite directions. The set of coordinates {(0, 1), (1, 0), (-1, 0), (0, -5)} is an example of the vertices of a kite. A rhombus is a quadrilateral with all four sides congruent. The more common shape name for a rhombus is "diamond". Since a rhombus also happens to have two pairs of congruent sides that are adjacent to one another, then it follows that a rhombus is also a kite. So, all rhombuses are kites, but not all kites are rhombuses.
• What if you don't have the measurement of the diagonal?
• A kite is just double of a triangle.Why not half the hight and use the formula for calculating triangle area without the multiplication by 1/2 as a kite is double of a triangle?
• It is not necessarily made up of two of the same triangle. Therefore you can’t just modify the formula for the area of a triangle. You have to find another formula.
• I got the same answer by finding the area of the triangle above, 28, and then multiplying by two (to reflect the area of the bottom triangle). Is this a good way to achieve the same result or is it better to try to convert the kite into a rectangle? Thank you.
(1 vote)
• That works fine, you are basically doing the same thing as Sal, you are doing A = 1/2 bh *2, so 1/2*2=1 and you end up with just A = bh. The final idea for Sal is that the area of a kite is given by A = 1/2 d1*d2 where d1 is one diagonal and d2 is the other. Kites also have diagonals that are perpendicular to each other.
• I don't really understand the formula of kite

What is it??
(1 vote)
• Just like a rhombus, A = 1/2 d1*d2 where d1 and d2 are the two perpendicular diagonals of a kite.
• If you just find the area of half of the kite and multiply that by 2 you would get the answer right?