how much water?

Is 3 cubic meters of water a lot or a little?

Typical engineer. Instead of giving you the amount of water in

terms of a measure that might actually make some sense, like

cups or spoonfuls or gallons, he’s talking about cubic meters. So,

how much is 3 cubic meters of water? A bathful? A pondful? A

swimming poolful?

Let’s start by think about what just 1 cubic meter actually is:

Volume of a cube = length x width x depth

Cubic meter = 1m x 1m x 1m

= 1m

3

A cube-shaped container with length, width, and

depth all of one meter holds exactly one cubic

meter of water.

So 3 cubic meters of water is the volume of water

you could store in three of those one meter cubes:

1m

1m

1m

Length

Width

Depth

1m

1m

1m

1m

1m

1m

1m

1m

1m

+

+

3 cubic meters =

278 Chapter 7

regular polygons

That’s true.

In fact, thinking about cube shapes can only take us

so far, because, aside from the square-shaped one,

the hot tub range isn’t made out of cubes.

OK—stop right there! I don’t know

how closely you’ve looked but I

don’t see any hot tubs that look like

they’re made out of CUBES.

How do the hot tubs compare to a cube?

Like a cube, all the hot tubs have a uniform depth. They

also have straight sides at a right angle to the base. But for

most of the shapes of hot tub, calculating the volume using

length × width × depth would give you the volume of a

box that you could fit the hot tub inside, not the water that

the hot tub would contain. It might be handy, but it’s not

what we’re looking for!

length

Same depth a

ll ov

er

T

he “T

r

i-cu

zi” tub.

width

depth

Volume of a hot tub = ? x depth

Length x width x depth is the

volume of the box that w

ould fi

t

around the hot tub.

What tool from your Geometry

Toolbox could we use to calculate the

volume, instead of “length × width”?

you are here 4 279

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