Head First 2D Geometry

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quadrilaterals

Business is booming!

Before too long, lots of new customers come flocking to the business.

Look again at the rectangle and triangles that make up a parallelogram.

What do you think you can do to speed up your calculations?

Here are a bunch of the

new lawns your customers

want to pay you to mow.

Nice work, but that’s a lot

of time you’re gonna spend in

the office calcuating costs,

isn’t it?

Fair enough.

You can’t bill customers if you don’t have time to actually mow

their lawns. There is probably a way to speed things up a bit.…

242 Chapter 6

study hall conversation

Jim: Well, a parallelogram is basically made up of just three

shapes, a rectangle and two triangles.

Frank: Yeah, but those two triangles look the same, right? So

maybe they’re congruent.…

Joe: Nice! So we could calculate one triangle area, multiply by

two, and then add on the area of the rectangle.

Jim: That’s still a few calculations per lawn, duh!

Frank: True. So I wonder if we could take it any further?

Joe: Maybe we can move these shapes around a bit. Could

we turn them into just one shape whose area we know how to

calculate?

So how can we speed

up the area calculation

for a parallelogram?

Joe

Frank

Jim

you are here 4 243

quadrilaterals

Geometry Magnets

Let’s see if we can figure out a