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## 5th grade

### Course: 5th grade > Unit 11

Lesson 4: Volume word problems# Volume word problem: water tank

Sal using volume of a rectangular prism to solve a word problem. Created by Sal Khan.

## Want to join the conversation?

- 1:56did anyone hear any slamming? Sounded like a door being closed really hard(20 votes)
- A rectangular container of oil is 20 cm long and 12 cm wide . It contains 1.680 l of oil . What is depth of the container?(9 votes)
- Well, V=lwh, which means volume is equal to length*width*hight (depth). Since we know the length, width, and volume; all we need to know is the depth. In order to figure that out, divide length*width on both sides of the equation (V=lwh to V/lw=h). So we now figure out
**how**to figure out the depth. Substitute the numbers into the equation, so 1.680 liters divided by 240 cm^2 (this number came from 20 times 12 which equals to 240). Since 1 liter is equal to 1000 cm^3, 1.680 liters is equal to 1,680 cm^3, so 1,680 divided by 240 cm^2 is equal to**7 cm**( the unit came from cm^3 divided by cm^2 which results in the linear unit cm).(15 votes)

- 0:51lol probably someone is mowing da lawn. XD(13 votes)
- He said it was a ¨helicopter or something¨ So you don't know(0 votes)

- how do you do it if one of the side lengths is missing because my problem says " A pool is filled with 270 cubic meters of water. The base of the pool is 15m long and 9m wide. What is the height of the water in the pool?" 😵😵(8 votes)
- Volume = Length (width) (height)

You were given volume, length and width.

Plug them into the formula in their respective spots, then solve for height.

Give it a try. Comment back if you get stuck.(9 votes)

- when i figure out you get energy points from videos i watch everyone of them to get points(11 votes)
- Is it pretty much getting the volume of both and then subtracting them?(11 votes)
- confusing but i can understand(8 votes)
- if I don't get a quiz all answers correct then I redo the quiz until the entire quiz is correct who heard the helicopter outside in the vidio he mention's it because I didn't hear anything.(7 votes)
- wont it be l*w*h(6 votes)
- hi peaple how is the covid 19 u guys ok i hope every body needs to be safe even for khan. everybody needs to be safe be carful everyone. stay safe. stay strong. stay nice.(6 votes)

## Video transcript

A water tank is 12 feet high,
5 feet long, and 9 feet wide. A solid metal box which is
7 feet high, 4 feet long, and 8 feet wide is sitting
at the bottom of the tank. The tank is filled with water. What is the volume of
the water in the tank? So let's think about this. We have a water tank. It's 12 feet high. I'll try to draw this
as good as I can. So it's 12 feet high. It's 5 feet long. So this looks like
that's about 5 feet. And it's 9 feet wide. So this is my best rendition
of what a tank looks like. So the tank might look
something like this. That is my water tank. Let me draw it, draw
the whole thing. So there is my water tank. And I'm going to make
it transparent so that we can see what's
going on inside of the tank. So here we go. There's like a helicopter
outside or something, I don't know if
you all hear that. But let's see. So there is my water tank
12 feet high, 5 feet long, and 9 feet wide. And then they say
there's a solid metal box which is 7 feet high, 4
feet long, and 8 feet wide sitting at the bottom. So let's see if I can draw that. So let's say it's 4 feet wide. Or I guess they say 4
feet long, 7 feet high. So let's see, 4 feet might
look something like this. It's 7 feet high, which might
look something like that. 7 feet high. Obviously, I'm not drawing
it perfectly to scale. 7 feet high and 8 feet wide. So it might look
something like this as it's sitting in this tank. So this is that metal box. And they say it's
a solid metal box. It's not like any
water can fit in here. So let me make it as
a solid metal box. So this is a solid metal box. And then I'm going to fill
the whole thing with water. I'm going to pour
water into this thing. And the water's going
to start filling up. And it's going to fill up
all the volume of the tank except where the metal box is. It's not going to be able
to fill in that volume because the metal box is solid. So it's going to fill up. We're going to fill it,
slowly fill this thing up around the metal box. So what's the volume that
it's going to fill up? Well, it's going to
fill up the volume of the tank minus the
volume of the metal box. It couldn't fill in
the metal box volume. So let's figure
out what that is. The volume of the
tank is going to be 9 foot by 5 foot times 12 feet. That's the volume of the tank. Tank volume. And from that, we want to
subtract the metal box volume. So minus 4 foot by
8 feet by 7 feet. This is 4 feet wide. It is 8 feet-- they
say it's 7 feet high. It's 4 feet long. And it's 8 feet wide. So this right over
here is the volume. I guess we could call
it the metal box volume. When you take the tank volume
and subtract out the box volume, that's how much the
water can actually fill in. So I only drew the
water partially filled. But once it's already
filled in, the water is going to go all the
way to the top here. And we'll fill in
everything except for where that blue box is. So let's figure out
what this value is. So 5 times 12 is 60. 60 times 9 is 540. And then in blue
here, let's see. 4 times 8 is 32. 32 times 7 is 210. Plus 14, which is 224. So it's minus 224. Minus 224. Did I do that right? I don't want to make
a careless mistake? So 32 times 7. 2 times 7 is 14. 3, which is really a 30 here. 30 times 7 is 210. Plus another 10 is 220. So 224. So this is going to be
equal to-- let's see. 500 minus 200 is 300. And then 40 minus 24 is 16. 316. And our units are in cubic feet. So the volume of the
water in the tank? 316 cubic feet.