814 Math (2010) or 841: surface area

Showing posts with label surface area. Show all posts

Sunday, February 6, 2011

Shenna's Surface Area Scribepost

Math textbook pages 186-187, questions 2, 4, 6, 8

2. You need to find it because the circumference of a circle is the length of a circle. You would need the length of a circle in order to find out the surface area of a cylinder.

Click Surface Area of a Cylinder to know more about it

Here's a video about Surface Area of a Cylinder

Calculate the Surface Area of a Cylinder

Cylinder Volume and Volume Problems

Thursday, February 3, 2011

Ysabelle's Surface Area Scribe

Pages 186-187

7. Do you prefer to find the surface area of a cylinder by using the sum of the area of each face or by using a formula? Give at least two reasons for your choice.

A: I prefer to use a formula because it is quicker and I'm less likely to miss a part of the calculation.

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

Container A:
diameter- 7 cm
height- 122 cm

radius- 3.5 cm

SA=2.π.r.r+2.π.r.h
SA=2(3.14)(3.5)(3.5)+2(3.14)(3.5)(122)
SA=76.93+2681.56
SA=2758.49 cm²

Container B:
diameter- 11 cm
height- 85 cm

radius- 5.5 cm

SA=2.π.r.r+2.π.r.h
SA=2(3.14)(5.5)(5.5)+2(3.14)(5.5)(85)
SA=189.97+2935.90
SA=3125.87 cm²

Container B required more plastic to make.

10. Paper towel is rolled around a cardboard tube. Calculate the outside surface area of the tube.

radius-2 cm
height- 27.5 cm

outside SA=2.π.r.h
outside SA=2(3.14)(2)(27.5)
outside SA=345.4 cm²

Cylinder Volume and Volume Problems

Solution:

JUMBO
r= d/2 r=20/2 r=10 cm V= πrrh V= [(3.14)(10)(10)](40) V= (314cm²)(40cm) V= 12560cm³

POPCORN LOVER'S
r=d/2 r=30/2 r=15 cm V= πrrh V= [(3.14)(15)(15)](20) V= (706.5cm²)(20cm) V= 14130cm³

Martha should buy Popcorn's Lover if she wants more popcorn for her money.

Solution:
outside
r=d/2
r=1/2
r=0.5m

V=πrrh
V=[(3.14)(0.5)(o.5)](10)
V=(o.785m²)(10m)
V=7.85m³
inside
r=d/2
r=0.8/2
r=0.4m

V=πrrh
V=[(3.14)(0.4)(0.4)](10)
V=(o.5024m²)(10m)
V=5.024m³

7.85m³-5.024m³=2.862m³ or 2.9m³

The volume of the concrete required to make the culvert is 2.9m³.

Tuesday, February 1, 2011

Surface area of a Cylinder

Cylinders
The base of a cylinder are circles, so first we have to review some basic termanology of circles:
-Radius
-Diameter
-Circumfrence
-Pi

Radius
-Half of diameter

Diameter
-Cuts circle in half

Circumfrence
-Perimeter of circle

Pi
-Ratio between circumfrence/diameter
-3.14

Now we have to review the different formulas for circles:
Cicumfrenc=∏.d=c
radius= d/2=r
diameter= 2.r or c/∏=d
Area of a circle= ∏.r.r

Net of a Cylinder:

This is a net of a cylinde

-The height is always given to you

-the base is the circumfrence the circles

-To calculate the surface area you have to add up the lateral area (LxW) and other formulas such as...

LxW

∏.r.r=A
d=2r
R=d/2
C=∏.d

For now, We are going to practice how to calculate the area, circumfrence, diameter, and radius of a circle. For these five circles, I had to calculate the area and circumfrence using the given radius or diameter. I had to plug in the given information into the formulas to find the area and circumfrence. This is how I did it.

For circle A and B, we have the given circumfrence but we have to find the radius, diameter and area. So what I did first was I found the diameter because once you have found the diameter or radius, you can find anything. I found the diameter by dividing the circumfrence by pi (3.14) and that gave me the diameter, then I could find the radius and area.

Here's a video on Surface area of Cylinders:

I hope you understand more about circles and cylinders, please notify my if I made any mistakes or if you have any suggestions for my post. Thanks!

Monday, January 31, 2011

Area of Rectangular and Triangular Prisim's

1. BxH/2

11x5/2=27.5cmx2=55

LxW

9x15=135x2=270cm

15x5=75cm

55+270+75=400

TSA=400cm

2. LxW

12x5=60x2=120cm

8x5=40x2=80cm

12x8=96x2=192cm

120+80+192=264cm

TSA=264cm

Thursday, January 27, 2011

Hanin's Surface Area Scribe HWB 3 Q's

HWB 3 Questions

Page 54-55

These are the answers to the questions I chose. I will show my work in the end.

1. Finding the sum of all the areas of each face on a 3-D object is called surface area.

2. a) 220.6 cm

b) 451.2

3. a) 120 m

b) 140.1

Here is my work:

Cylinder Volume and Volume Problems

1) (question 12 from 7.3 in the textbook)

Jumbo
r=d/2
r=20/2
r=10cm

v=3.14xrxrxh
v=(3.14x1ox10) x40cm
v=314cm^2 X 40cm
v= 12560cm^3

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

v=3.14xrxrxh
v=(3.14x15x15) x20cm
v=706.5cm^2 x20cm
v=14130cm^3

Martha should buy the Popcorn Lovers container
it has more.

2) (question 7 from &.4 in the textbook)

Metre convert to centimetre:
0.25m=25cm
1m=100cm
0.4m=40cm
0.35m=35cm
1.4m=140cm

Volume of cylinder

r=d/2
r=25/2
r=12.5cm

v=3.14xrxrxh
v=(3.14x12.5x12.5) x100cm
v=490.625cm^2 x100cm
v= 49062.5cm^3

Volume of triangular prism

v=bxh/2xh
v=40x35/2 x140cm
v=700cm^2 x140cm
v=98000cm^3

Answer:
98000cm^3
-49062.5cm^3
=48937.5cm^3

Homework Book Pages 52 - 55

Page 53

Page 54

2. a)

* If you can't read the picture (;

5 x 3.2 = 16

5 x 11.5 = 57.5

11.5 x 3.2 = 36.8

16 + 16+ 57.5 + 57.5 + 36.8 + 36.8 =220.6 cm2

TSA = 22o.6 cm2

Cylinder Volume and Volume Problems

v= b x h^1 /2 x h^2
v= 12 x 15 / 2 x 15
v = 1,350cm^3

My assumptions is that the volume of the cheese from the block is 1,350 cm^3

Outside
d/2 = o.5m^2
v=π.r.r.h
v=3.14.o.5.o.5.10
v=o.785m^2.10
v=7.85m^3

Inside
d/2=0.4m^2
v=π.r.r.h
v=3.14.0.4^2.10
v=5.024m^3

7.85m^3 - 5.85m^3 = 2.86^3 or 2.9m^3

The volume of the culvert is 2.9m^3

Wednesday, January 26, 2011

Shane's Scribe Post

Questions Number 3 and 5

3.) Find the surface area of this right rectangular prism to the nearest tenth of a square centimetre

Surface Area= 2(18.5)(13.5)+2(18.5)(5)+2(13.5)(5)
= 499.5+185+13 = 697.50 cm

5.) Calculate the surface area of this ramp in the shape of a right triangular prism.