Math Is Fun Forum

blue44

Member

Registered: 2008-09-14

Posts: 2

Please help! Calculate surface area of a toblerone!

I am trying to calculte the surface area of a toblerone shaped object but am stuck :
Length = 10cm
Height = 3cm
Width = 4 cm

Please help!

Last edited by blue44 (2008-09-14 03:34:37)

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Please help! Calculate surface area of a toblerone!

Is the shape something like this?

blue44

Member

Registered: 2008-09-14

Posts: 2

Re: Please help! Calculate surface area of a toblerone!

Hi Jane
Yes this is the shape I am struggling with!

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Please help! Calculate surface area of a toblerone!

The surface area is made of 5 shapes - two triangles at each and, and three rectangles around the sides.

The area of the triangle is easy to find since you are given the base length and height.
Using A = bh/2, the area of each triangle is 3*4/2 = 6.

The rectangles are a little trickier, since you need to work out their width first.
The rectangle on the bottom has a width of 4 (since the triangle has a base length of 4), and for the other two you need Pythagoras.
Splitting the triangle down the middle gets you a right-angled triangle with short lengths of 2 and 3.
Therefore, the hypotenuse must be √(2²+3²) = √13.

So there are two rectangles with a width of √13, which will have an area of 10√13, and one rectangle with a width of 4 which has an area of 40.

Adding it all up gives an overall surface area of 6+6+40+10√13+10√13 = 52+20√13 ≈ 124cm².

---

Why did the vector cross the road?
It wanted to be normal.

blue44

Member

Registered: 2008-09-14

Posts: 2

Re: Please help! Calculate surface area of a toblerone!

Thank you, thank you, thankyou!  This answer was so clear and well explained

I had spent so much time trying to find the answer and nothing made sense to me before.  Thank you!