Lesson Planning

Lesson Planning 101

2. Area of Triangles

Dad: Do you need any help with your homework?

Kid: No, I just have to study for my math test tomorrow.

Dad: Well, maybe I can help? I was pretty good at math when I was in school.

Kid: Sure.

Dad: What is your test on anyway?

Kid: It is on area of triangles, rectangles and parallelograms.

Dad: Ok, all you have to do is memorize the formulas then. For a rectangle it is Length x Width, for a square it is Length x Width, for a parallelogram it is Base x Height and for a triangle it is one half Base x Height.

Kid: Well, that’s a lot of formulas to remember. Did you know that all parallelograms are made up of two triangles that are the same? (kid demonstrates two triangles make a parallelogram)

Dad: Well, that is interesting isn’t it?

Kid: Yeah, so that’s why a triangle’s area is HALF Base x Height!

Kid: Yes! And did you also know that all parallelograms can be turned into rectangles?

Dad: Really? Show me how?

Kid: Well, if you go to one corner on the bottom and draw a height line to the opposite side, it makes a small triangle that if you cut it off, it fits like a puzzle onto the other side to make a rectangle.

Dad: Well what do you know!!!

Kid: And since the area of a rectangle is Length x Width, it’s really the same as Base x Height.

Dad: Now that is interesting.

Kid: So, really, I only need to remember Length x Width, the rest of these shapes is using that formula to find area.

Dad: You’re so smart!

Kid: And, so now I am done studying and I’m going out to play!


Who’s to say... you need to memorize...
Well that’s just silly, easier than that cause
I can promise, it’ll all make sense soon
and  you’ll realize, no need to compromise

triangles, aren’t as difficult
as you make-em, lets find the area
so let’s look at, a quadrilateral shape where
length times width, is all you need for area

 All you have to do is break it dowwwn....
Then you’ll see how easy it can be
And no need to memorizzze,
Then you will see its as easy as 1,2,3

So we have, length times width as area
But be aware, base times height it’s just a
Another way, to say the same thing so
 we just say, area is base times height

notice that, two triangles make up
that same polygon, so area of a triangle
is just half of the, the base times height of a
 full polygon, its just that easy that