## Monday, February 7, 2011

### Text Book Questions

Question 9:

Kaitlyn and Hakim each bought a tube of candy. Both containers cost the same amount. Which container required more plastic to make?

Candy tube A:

d/2 = r

7/2 = r

3.5 cm = r

TSA= (2 x Pi x r x r)+(2 x r x Pi x h)

TSA= (2 x 3.14 x 3.5 x 3.5)+(2 x 3.5 x 3.14 x 122)

TSA= (76.93cm2)+(2681.56cm2)

TSA= 2758cm2

The amount of plastic needed to make tube A is 2758cm2.

Candy tube B:

d/2 = r

11/2 = r

5.5 cm = r

TSA= (2 x Pi x r x r)+(2 x r x Pi x h)

TSA= (2 x 3.14 x 5.5 x 5.5)+(2 x 5.5 x 3.14 x 85)

TSA= (189.97cm2)+(2935.9cm2)

TSA= 3125.87cm2

The amount of plastic needed to make tube B is 3125.87cm2.

The tube of candy that needs more plastic is B.

Question 10:

Paper towel is rolled around a cardboard tube. Calcula

te the outside surface area of the tube.

d =2r
d =2 x 2
d =4cm

c = Pi x d
c = 3.14 x 4
c = 12.56cm

l x w = area of a square
12.56 x 27.5 = area of a square
345.4cm2 = area of a square

The out side surface area of the tube is 345.4cm2.
Cylinder Volume and Volume ProblemsQuestion 1:

Jumbo Popcorn

d/2=r
20/2=r
10cm=r
v=(pir^2)h
v=(3.14x10x10)40
v=314cm^2x40cm
v=12650cm^3

Popcorn lover's

d/2=r
30/2=r
15cm=r

v=(pir^2)h
v=(3.14x15x15)20
v=706.5cm^2x20cm
v=14130cm^3

Here is my math video

If Martha wants to get more popcorn for her money she should by the popcorn lover's container.

Question 2:

d/2=r
10/2=r
5cm=r

v=(pir^2)h
v=(3.14x5x5)40
v=78.5cm^2x40cm
v=3140cm^3

d/2=r
8/2=r
4cm=r

v=(pir^2)h
v=(3.14x4x4)40
v=50.24cm^2x40cm
v=2009.6cm^3

3140cm^3 - 2009.6cm^3=1130.4cm^3

1. Good job Marysa! I like how your post is easy to read. Your work was clear and easy to understand. Next time, add more color, videos, and links.

2. Great job Marysa! I like how your post is very organized. The picture that you put really popped out. Next time you might want to include a video and/or link.

3. Good job Marysa! I like how your post is so neat! I really like your picture! Next time you should try to add a video if you can so other classmates in grade eight can understand..Other then that your post was really great!