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

Lesson 2: Volume with fractions

# Volume with fractional cubes

Another way of finding the volume of a rectangular prism involves dividing it into fractional cubes, finding the volume of one, and then multiplying that volume by the number of cubes that fit into our rectangular prism. Created by Sal Khan.

## Want to join the conversation?

• I don't understand how 1/4*1/4*1/4 equals 1/64. Doesn't timesing usually make the number bigger!?
• It usually does make things bigger but with fractions, it does not. Because 1x1x1 is equal to one and 4x4x4 is equal to 64. One is the numerator and 64 is the denominator. So it is 1/64. If 64 was the numerator then it would be bigger because 64/1 is equal to 64.
• I am still very confused and I've watched this video 3 times. I just still don't understand the steps that you need to do when doing these questions.
• Well, first you have to figure out the volume of one cube (e.g., 1/4*1/4*1/4=1/64), then you have to figure out how many cubes there are in the figure. Because the volume of one cube isn't one, you would then multiply the number of cubes by the volume of one cube. This way you would get the volume of the whole cube. Hope that helps!
• I still do not understand the fact that if on of those small cubes is 1/4 ft and the volume is 1/4 cubic ft which is 1/64 cubic feet, why does it seem that the volume is less than the size of the cubes that are definitely smaller than the volume?
• Each small cube has a volume of 1/64 cubic feet. The prism as a whole has a volume of 1/4 cubic feet and:
1/64 < 1/4
Thus the prism has a greater volume than its constituent cubes as desired!
• Ehhh.... I don't get this! Please help! I'm confused.
• I need help. I don't get how the video and the quiz don't even say the same thing
• I think this video will help get part of the quiz done.
• He is making it sound much more complex than it really is
• As I like to say, the more detailed the explanation, the more detailed the understanding.
• This does not make sense at all!! Joshua can you help me find the area of a prism well I mean can you tell me how to find an area of a prism?! :)
• I get the part of finding the volume but I still don't get how you find the amount of cubes of a certain measure that should be inside of a 3-Dimensional figure. I usually understand math, but this part really triggered me and I still don't know why or how.