## Thursday, October 7, 2010

### Elaine's Scribepost for October 5, 2010

Hi you guys! We each were assigned a question to do for the blog and the question I got was the one with the picture of the house.

The question was :

The surface area of walls, roofs, doors, and windows all affect the amount of heat loss from a house. Calculate the surface area for the doors,windows, walls, and roof for the house below. Express each answer to the nearest tenth of a square metre.

wi
ndo
ws = 80cm x 60cm each
doors = 205cm x 82
cm each
-back of the house is identical to the front
-sides of the house are identical to each other

I started off with the windows. Since there are 3 window in the front and 2 window on the side, and the opposite sides are equal there would be 10 windows all together [(3+2)(2)]

Here is how I got the area of the windows:

First, I converted the centimetres into metres by dividing it by 100
80/100= 0.8m
60/100= 0.6m

SA = 10(lw)
= 10(0.8 x 0.6)
= 10 (0.48)
= 4.8 squared m

Now, I will calculate the area of the doors. Since, the back and front of the house are both identical, there would be 2 doors :

I also had to convert the cm in m:

SA = 2 (lw)
= 2 (2.05 x 0.82)
= 2 ( 1.68)
= 3.36 squared m

For me, finding the area of the walls got a little tricky. What I did was find the sides of the walls, then subtracted the area of the doors and windows:

SA = 2 (lw) = 2 (lw)
= 2 ( 4.8 x 2.5) + (2.5 x 7)
= 2 (12) + 2 (17.5)
= 24 + 35
= 59 squared m

- after adding everything, together, I had to subtract the area taken up by the windows and doors.
-the area of the doors was 3.36 squared m
- but for the windows, only 8 are on the walls so I had to find the surface area of 8 windows:
SA = 8 (0.8 x 0.6)
= 8 (0.48)
= 3.84 squared m

SA = 59 - 3.36 - 3.84
= 51.8 squared m

Lastly, I have to find the area of the roof I did that using two different steps, the rectangles, then the triangles:

SA = 2(lw)
= 2 (7 x 4)
= 2 (28)
= 56 squared m

now I find the area of the triangles:
-SA =2 (b x h/ 2)
- but since the formula is multiplied and divided by two, they both cancel out
-SA = b x h

SA = b x h
= 4.8 x 3.2
= 15.36 squared m

SA = 56 + 15.36
= 71.36 squared m

-but after adding the two, I have to subtract the area of the two windows
-SA= 2 (0.8 x 0.6)
= 2 (0.48)
= 0.96

SA = 71.36 - 0.96
= 70.04 squared m

After all the work that's done, the answers are:

Windows = 4.8 squared metres
Doors = 3.36 squared metres
Walls = 51.8 squared metres
Roof = 70.04 squared metres

That is how I got all my answers. Sorry if it's kind of confusing and THANKS FOR READING MY SCRIBE