Thread: Areas and Perimeters?

I did these problems, teacher said they were wrong and sent me away to do them again. I tried and still got the same answers.
*

A) Find the perimeter to the figure
B) The Enclosed area:

Picture:

12002.jpg picture by EdenJonas - Photobucket

Thanks

Hello,

Originally Posted by suckatmaths

I did these problems, teacher said they were wrong and sent me away to do them again. I tried and still got the same answers.
*

A) Find the perimeter to the figure
B) The Enclosed area:

Picture:

12002.jpg picture by EdenJonas - Photobucket

Thanks.

Please provide the results (and the working) you got. It would be easier to see where the mistakes are, if there are any. What do you find ? I have the answers...

A) 10squared + 8squared=
100+64
=164
=squareroot164 = 12.80

10+8+12.80 = 30.8cm.

(see? I suck)

B) 1/2 12.80x8

6.4x8
=51.2

I did really bad.
There is just this major question mark next to them.

Originally Posted by suckatmaths

A) 10squared + 8squared=
100+64
=164
=squareroot164 = 12.80

10+8+12.80 = 30.8cm.

(see? I suck)

B) 1/2 12.80x8

6.4x8
=51.2

I did really bad.
There is just this major question mark next to them.

Okay, your mistake comes from the application of the Pythagorean theorem.


In a right angle triangle, the hypotenuse is the longest side. It is also the side opposit to the right angle. So here, the hypotenuse is the side which length is 10.
And the Pythagorean theorem says

Hence the length of the third side is not , but... ?

6squared? :\
I'm sorry, I am really bad at this.

Oh wait, is it = 10squared = 8squared + 6squared?

Originally Posted by suckatmaths

6squared? :\
I'm sorry, I am really bad at this.

Oh wait, is it = 10squared = 8squared + 6squared?

Yes

So the length of the third side is 6 ! (not 6squared... read carefully the formula from the Pythagorean theorem)

So therefore do I just:

10squared + 8squared + 6squared = perimeter?

Then squareroot = perimeter?

Originally Posted by suckatmaths

So therefore do I just:

10squared + 8squared + 6squared = perimeter?

Then squareroot = perimeter?

Okay... It looks like you have big problems with basics


The perimeter is the sum of the sides that are on the outside.
This means that the perimeter of your figure is 8+10+the length of the semicircle.
You're not asked for the perimeter of the triangle !!!

Now, do you know the formula for the perimeter and the area of a circle ?
What is the radius of this semicircle ?


The perimeter of the triangle would be 8+10+6.
Not with the squares. Please read carefully the formula from the Pythagorean theorem !

Radius of the semicircle is 3.

Do I go: 3*pi = 9.42m

Then add: 9.42 + 10 + 8

The perimeter = 27.42m?

Originally Posted by suckatmaths

Radius of the semicircle is 3.

Do I go: 3*pi = 9.42m

Then add: 9.42 + 10 + 8

The perimeter = 27.42m?

Exactly !

But did you understand the path to come up with this solution ?

Yay, it only took me forever. Ahahaha.
Thank you for all your help on that one.

Originally Posted by Moo

Exactly !

But did you understand the path to come up with this solution ?

Yes, I finally got there. I have to READ the question, and work out everything... The perimeter of not JUST the triangle, but the circle aswell.
So thank you.