So far, we've used the formula...
You may also see this written as
'bh' written together like this
means base x height
If we do this one:
Now that we've done the multiplication step...
We KNOW the area is 12cm squared
We'll put this over here
and get a duplicate triangle.
Cut it in half down the middle
If I flip this part over...
We can put it back together
and make a rectangle.
The height is still 6
And 2x6 gives an area of...
We can write a new formula
to describe this math.
Half base x height
We don't meet THIS formula first
because some people
find it a bit confusing
when written this way.
I don't want you to be confused
but I DO want you to know
that you might see it like this as well.
And if you do...
you know what it means!
Let's do another one.
Here we've got a base of 3
and a height of 4.
You might say to me...
But, get this!
Now THAT makes a difference, doesn't it?
So we can decide
that THIS is the base
and THIS is the height!
And also...
Of course
I'm not halving THIS base!
You know why!
I'm halving the height instead!
It's quicker than the bxh/2 formula.
This is the alternative formula at work
But...
It's NOT the shortcut I promised you last time!
That's coming next...
And it's actually in the ORIGINAL formula!
Here's my triangle
And we're all ready to go.
We know we can divide EITHER base
OR height by 2
Well then!
Here comes the shortcut!
And now: 5 x 6
Set out for the original formula
and reduce EITHER base
OR height
NOT both!
by this factor of 2
And of course
that gets rid of the denominator!
Then just multiply
And there's the area!
1 line of math ONLY... Nice!
Base is 7
x height
of 24
And we get...
How about THAT for a time-saver!
Have fun, see you soon!