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### Course: Grade 7 (Virginia)>Unit 7

Lesson 5: Applying surface area & volume

# Volume word problem: gold ring

See if you can find the incremental volume of a ring in cubic inches. You'll need to put to use your knowledge of how to measure volume. Created by Sal Khan.

## Want to join the conversation?

• why would the water move up that amount if there is a hole in the center of the ring? Wouldn't that hole fill up and change the amount of space the water takes up?
• We are interested in the volume of the "gold". The hole in the ring fills up with water but the gold doesn't. So the water displaced by the ring is the volume of the gold
• Wouldn't the volume of the ring be just 0.25 cubic inches? as the ring does not have a length of 3 inches and width of 2 inches?
• The water level rises by 0.25 inches.
If you get 0.25 inches (height added) and multiply it by length and width (2 and 3) You get the total amount of water dispaced, which is the area of the ring. If you multiply your length times your width,(3x2) you get 6. 6 times 0.25 extra height =1.5 or *6 x 0.25 = 1.5
---Hopefully this makes it a little bit easier---
(1 vote)
• At , How come the inches in the water increase?
• the ring's volume is 1.5, so it displaces the water so it stays even, Because atoms cant go inside of each other...
• I have 2 questions. How could volume be in cubic inches? Why do you need to leave out the '4' in the height when solving for the mass of the ring?
• should you always divide the biggest number by the smallest number in whatever volume problem you are doing? Also, what is the formula for volume problems? Because it wasn't explained in the video, I ended up getting the problem wrong.
• So, basically, you can find the volume by finding the biggest object, then subtract the space that isn't the smaller object inside, right?
• how do you find the area of a square.
• Width squared.
Think of it like a line 3 inches long 3 times, as an example.
• so you can know the ring's volume just like khan said at ?
• Yea dude use the method he taught you in the video.
(1 vote)
• how to find area of box
(1 vote)
• A box is a 3D object, so you can either find the volume or the surface area, but there is no such thing as area of a 3D object.