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## 6th grade

### Unit 10: Lesson 3

Volume with fractions- Volume of a rectangular prism: fractional dimensions
- Volume by multiplying area of base times height
- Volume with fractions
- How volume changes from changing dimensions
- Volume of a rectangular prism: word problem
- Volume word problems: fractions & decimals

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# How volume changes from changing dimensions

Sal discusses changing dimensions on a rectangular prism affects its volume.

## Want to join the conversation?

- 4:10it will be multiplied by 8(5 votes)
- Yes it is cause 2*2*2 =8(2 votes)

- This stuff good 👍(4 votes)
- 1:04i don't understand(3 votes)
*He means 2 * 3 * h, where h is the height.*

When he substituted 5 for h, he replaced the h in 2 * 3 * h with 5.

Now the expression is 2 * 3 * 5.(3 votes)

- My FLVS flex geometry honors class brought me here.(4 votes)
- you said this at the one minuet and eight second in the video why does the three stay the same?(2 votes)
- Why do the call it 3D I mean if there is a 3rd Dimension there has to be millons ands millons more demensions right?(2 votes)
- ummm. we live in a 3D world. there is a 4th dimention which is time.

the string theory, however, suggests that there are 10, 11 or even 26 dimensions. but so far, it hasn't been prooved.(4 votes)

- When volume remains constant what is the impact on the surface area of a rectangular prism of a change in the dimensions(2 votes)
- Surface area and volume are not the same. You may want to check out the surface area section. But, if you maintain volume, and change one dimension, you will have to either increase or decrease another dimension to make this happen.(2 votes)

- So, in school we are learning about change in dimensions and my teacher makes it so confusing with a whole bunch of formulas like new area over old area and I just don't get it can someone explain it for me in a more simpler way?(2 votes)
- If you double one of the dimensions, say change one side from 2 to 4 it doubles the volume. if you were to do this to any side, say double it, it would double the volume. The box was 2x3x5. If you double any of those numbers, it doubles the volume. A 2x3x5 box has a volume of 30. If you doubled the 2 to a 4 making it a 4x3x5 box, the volume becomes 60. Lets say you changed the one side from 5 to 10 making it a 2x3x10 box, same thing , volume goes from 30 to sixty. Lets say you changed the one side from 2 to 8, essentially 4 times its original length. now the box is 8x3x5. It will make the volume 4 times as much also. the volume would go from 30 to 120. hope this helps. :)(2 votes)

- Any chance the video could finish the information presented?

Leaving off the answer & its description was completely unhelpful. Sal asked a question, but never provided the information after4:13. I am disappointed.(2 votes) - Is there anyway to figure out the height of the rectangular prism using only the 2 and 3 (width and length I think?)?(1 vote)

## Video transcript

- [Tutor] I have a rectangular prism here. We're given two of the dimensions. The width is two, the depth is three, and this height here, we're
just representing with an h. And what we're gonna do in this video is think about how does the volume of this rectangular prism change as we change the height. So, let's make a little table here. So, let me make my table. So, this is going to be our height, and this is going to be
our volume, V for volume. And so, let's say that the height is five. What is the volume going to be? Pause this video and see
if you can figure it out. Well, the volume is just going to be the base times height times depth, or you can say it's going to
be the area of this square, so it's the width times
the depth which is six times the height. So, that would be two
times three times five. So, two times three times five which is equal to six times five which is equal to 30, 30 cubic units. We're assuming that these
are given in some units, so this would be the units cubed. Alright, now let's think about it if we were to double the height. What is going to happen to our volume? So, if we double the
height, our height is 10, what is the volume? Pause this video and see
if you can figure it out. Well, in this situation, we're still gonna have two times three, two times three times our new height, times 10. So, now it's gonna be six
times 10 which is equal to 60. Notice, when we doubled the height, if we just double one dimension, we are going to double the volume. Let's see if that holds up. Let's double it again. So, what happens when
our height is 20 units? Well here, our volume is still gonna be two times three times 20, two times three times 20 which is equal to six times 20 which is equal to 120. So, once again, if you
double one of the dimensions, in this case the height, it doubles the volume. You can think of it the other way. If you were to halve, if you
were to go from 20 to 10, so if you halve one of the dimensions, it halves the volume. You go from 120 to 60. Now, let's think about
something interesting. Let's think about what happens if we double two of the dimensions. So, let's say. So, we know, I'll just
draw these really fast, we know that if we have a situation where we have two by three
and this height is five, we know the volume here
is 30, 30 cubic units. But now, let's double
two of the dimensions. Let's make this into a 10 and
let's make this into a four. This is gonna look like this. This is going to be a four. This is still going to be a three. And our height is going to be a 10. So, it's gonna look something like this. So, our height is going to be a 10. I haven't drawn it perfectly to scale. Hopefully, you get the idea. So, this is our height at 10. What is the volume gonna be now? Pause this video and see
if you can figure it out. Well, four times three is 12 times 10 is 120. So notice, when we doubled
two of the dimensions, we actually quadrupled, we actually quadrupled our total volume. Pause this video and think
about why did that happen. Well, if you double one dimension, you double the volume. But here, we're doubling one dimension and then another dimension, so you're multiplying by two twice. So, think about what would happen if we doubled all of the dimensions. How much would that increase the volume? Pause the video and see if
you can do that on your own. In general, if you double
all of the dimensions, what does that do to the volume? Or if you halve all of the dimensions, what does that do to the volume?