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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