## Tuesday, October 5, 2010

### Riemer's Blog Post ;)

Hello everyone!

We were all assigned questions from the math textbook. Mr.Backe gave me the following question: The bottom of the prism shown is glued on top of the box such that it does not
overhang an edge. What is the surface area of th
e composite shape ?

First you have to find the area of the rectangular prism.
The rectangular prism has a length of 9cm, a width of 6cm, and a height of 3cm.

area of rectangular prism
=2(lxw)+2(lxh)+2(wxh)
=2(9x6)+2(9x3)+2(6x3)
=2(54)+2(27)+2(18)
=108+54+36
=198

Second, you will have to find the area of the triangular prism.

area of triangle
=2(bxh)/2
=2(4x3.5)/2
=2(14)/2
=2(7)
=14

area of rectangle
=2(lxw)
=2(7x9)
=2(63)
=126

Then, since the triangular prism is positioned on top of the rectangular prism, you must find the base of the triangle, and then subtract it from the area of the rectangular prism.

area of triangular prism (base)

=4x7

=28

Then you subtract it from the rectangular prisms surface area

=198-28
=170

Then you add it all up and end up with the surface area of the composite shape:
170+126+14

310