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### Course: Geometry (FL B.E.S.T.)>Unit 9

Lesson 7: Density

# Area density

Area or surface density is the amount of a quantity (often mass) per unit of area. Density=Quantity/Area. Created by Sal Khan.

## Want to join the conversation?

• The real takeaway from that situation is Tigersville animal control is underfunded.
• For real.
• Quick question on one of the practice problems:

The city limits of Las Pythagoras form a perfect shape of an isosceles right triangle whose legs are both 25 kilometers long.

In the solution, it says that the area is (1/2)(25 squared). How is this possible if the base isn't given in the question?
• The base is given, they just don't call it that. A right triangle can be oriented so one of the legs is the base and the other is the height. Because the lengths of both legs are 25 km, and they can serve as our base and height, the area would be (1/2)(25km)^2 or 312.50 square kilometers.
• wait so how did that work y Andrew was wrong when my dog ate my homework like that's crazy.
• i do not know
• What if it is finding the area?
• To find area from density and quantity, all you have to do is multiply the quantity divided by the density, and you have your area. Hope this helps!
• First question! How do you find the area of a cone? Cylinder? And sphere?
• As Kim said, you can find those in the search bar or some other sub category to hs geometry. Here's the link for cylinders (found off an EOC review guide) https://www.khanacademy.org/exercise/solid_geometry
• why doesn't he put the 144 into the area slot for the density equation?
• Because he is trying to find quantity, not density, so he multiplied both sides by area to solve for quantity.
• What can be a unit?
• Does anyone else think this question is catty?
(1 vote)
• No, why?
(1 vote)
• what is going on in tigersville??
(1 vote)
• when the questions says with two parallel boundaries 12km apart, I thought they meant from left to right from each other not from bottom to top which is height ?