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### Course: Geometry (all content)>Unit 8

Lesson 6: Surface and volume density

# Density word problem: blimp

Sal solves a word problem about the number of passengers a blimp can carry, using his knowledge of volume and density. Created by Sal Khan.

## Want to join the conversation?

• Ok, this problem makes sense and is fairly easy to grasp. But none of the questions on the actual worksheett (for lack of a better term) are like this? Even when i miss the question and walk through it with the instructions, it still doesnt make any sense and the rules seem to very. Does anyone know how to get through this because I cant make a lick of sense out of this.
• This video does not help me with the practice problems at all.
• What are blimps?
• Blimps are aircrafts filled with gas lighter than air (helium), which gives them the ability to float.
• I'm still having trouble understanding. Can someone please explain density to me??
• Density is (loosely) a measure of how much stuff is packed into an object. We can calculate it as mass/volume.

Consider a ping-pong ball and a ball of lead the size of a ping-pong ball. The lead ball is the same size, but much heavier. So we say that the lead ball is much more dense than the plastic.
• At , why in the 10^5 not subracted from 10^5?
• Because 10^5 is just shorthand for 100,000
2.2x10^5 - 2.11x10^5 = 0.09x10^5
translates into
220,000 - 211,000 = 9,000
If you remove the 10^5, then you're left with just 0.09, rather than 9,000.
• I'm not sure, but I think the answer should be 89 people or less. If it were 90 people the blimp wouldn't be able to get off the ground...
• I am really struggling in the "Practice: Density word problems". Can someone recommend me online practice problems that would help my understanding better.