Circle Graphs

A circle is a graph that represented data using sections of a circle.

sector - section of a circle formed by 2 radii and the area of a circle connecting the 2 radii.

eg.
Pets of students in Mr. W's class (24students)
1. What is the tittle?
2. What are the different categories represented by graph?
3. What percent of the class has a dog? and how many students have a dog?
4. % of class with cat? how many students have a cat?
5. What % of the circle is represented by all the sectors?
6. Would this graph make sense if the title or a sector labels were missing?

Video:
http://www.youtube.com/watch?v=jFg-e51Rhv4
Link:
http://socrates.bmcc.cuny.edu/cpe/circle_pie.html

Hope this helps!
thanks.

Lance's Scribe

Find the diameter of a circle with a radius of 12.6m.
Show the formula you used and all the work.
d=2r
d=2(12.6)
d=25.2m.♫♫♫

Find the radius of a circle when the diameter is 10.5cm.
Show formula and work.
r=d/2
r=10.5/5
r=5.25cm.♠

Find the circumference of a circle with a diameter of 3mm.
Show formula and work.
c=pi d
c=(3.14)(3mm)
c=9.42 mm.♦

Find the circumference of a circle with a radius of s.m.
Show formula and work
c=2pi r
c=2(3.14)(5)
c=10 314
c=c=31.4m.♥

Find the diameter of a circle with a circumference of 12.56 cm.
Show formula and work
d=c/35
d=1256/3.14cm
d=4cm.☻

Find radius of follow circles
d=4cm
d=10cm
c=15.7m
c=3.14cm. ☺

Lance's Blog

Area

Area
-the space a shape takes up
-described in square units eg. 4cm²

Review

Area of square or rectangle

Length x width
A=lxw

=6x2

=12cm²

Parallelogram

Base x Height

eg. the base 10cm and the heght is 5 cm

A=bxh
A=10x5

A= 50 cm²

Finding the Area of a circle

Use pieces of circle to create a shape very close to a parallelogram.

Close to parallelogram

H=Radius

B=½ circumference

Ap=bxh

Ao=2 pi r ÷2 x r

Ao=pi xrxr
The simple formula is Ao=pi r²

*Sorry the pi symbol doesn't work.

Find the Area of a circle with the radius of 10m.Show formula and work.

Ao=pi r²

Ao=3.14xrxr

Ao=3.14x100

=314m²

Find the Area of the following circles

the first circle has the radius of 8cm

the 2nd circle has the radius of 14.8m

Ao=pi r²
Ao=3.14x8x8
Ao=3.14x64
=200.96cm²

Ao= pi r²

=3.14x14.8x14.8
=3.14x219.04

=687.79m²

To find the Area of a circle,and the question gives you the diameter.

You should divide it into 2.After you find the quotient use formula to answer the question.

Check out this site:
http://www.mathplayground.com/
Check out this video

Circles

Parts of the Circle:

- center
- radius
- diameter
- circumference -is the distance around a circle
- usually represented by c
- this is a linear measurement

π = pi - the ratio of the circumference of a circle to its diameter. π2 = c/d
π = 3.14

Formulas : π = c/d c = πd d = c/π

Circumference of a Circle

Video:

Circles

radius - distance from the centre of the circle to the outside edge. represented by small b

diameter - distance across a circle through its centre . represented by small d

a diameter is 2 radii d=2r r=d/




construct a circle a radius of 4cm
1. start with centre of circle
2. measure the length of radius on a string
3. pencil at one of string and pin the sting in the centre of the circle.
4. trace an ARC around the centre

using a compass
1. measure a line the length of a radius
2. sharp line of compass in the centre of circle
3. pencil at the other end of the line
4. draw an ARC around the centre


TEXTBOOK:
page 270 - 272
# 1 -15 odd then even

PS:
feel free to comment and tell me ifIi did any mistakes or miss some parts.
thanks.

Adding Mixed Numbers

1 5/6 + 1 5/6 =
1 + 1 + 5/6 + 5/6 =
2 + 5/6 + 5/6 =
2 + 10/6 =
2 6/6 + 4/6 =
2 + 1 + 4/6 = 3 4/6 = 3 2/3









steps:
1. add the whole numbers
2. find common denominator for fractions
3. add the fractions
4. add the whole numbers to the fractions

eg.
1 1/3 + 2 1/3 = 3 2/3

3 1/6 + 2 5/6 = 5 6/6 = 6

3 2/3 + 2/3 = 3/43 = 4 1/3

eg.
1 1/2 + 2 1/3 = 3 2/6 = 3 1/3

2 1/2 + 4 1/6 = 6 4/6 = 6 2/3

homework:
page 249
# 1 - 3

PS:
If I did any mistakes or miss some parts, feel free to comment and tell!
thanks.

Subtracting Mixed Numbers

If you have like denominators, like

2 3/4 - 1 1/4,

then use fraction strips.

eg.

1 2/4 in lowest terms is 1 1/2

Second Method

Subtract the whole numbers,

2 3/4-1 1/4 2-1=1

then subtract the fractions

3/4-1/4=2/4

1 2/4 in lowest terms is 1 1/2

a) 2 2/3-1 1/3=1 1/3 b)3 7/8-1 3/8=2 4/8= 2 1/2 c)4 3/4-1/4= 4 2/4= 4 1/2

Subtracting Mixed Numbers With UNLIKE Denominators
3 3/8- 1 1/2 3=24/8 1=8/8

27/8-12/8=15/8=1 7/8

Another Way to Regroup

3 3/8-1 1/4

2 11/8-1 4/8 (borrowed 8/8 or 1 from 3)

=1 7/8

a)4 1/4-3 2/5 b)4 1/4-7/8

4 5/20-3 8/20 4 2/8-7/8

3 25/20-3 8/20 3 10/8-7/8

=17/20 =3 3/8

This concludes my blog about subtracting mixed numbers but remember...

Pi day is on Tuesday March 16 at lunch time.

Clues will be all over the school and the first person to find all of them and get to the final destination will win a prize.

Good luck, and Good Bye!

Subtracting Fractions with Unlike Denominators

* You must find a common denominator or LCD & use equivalent fractions.

eg. 3/4 - 1/2 = 1/4
solution :

3/4 = 3/4
-
1/2 = 2/4
___
1/4

2/3 - 1/4 = 5/12
solution :

2/3 = 8/12
-
1/4 = 3/12
____
5/12

3/4 - 2/4 = 1/4
solution :

3/4
-
2/4
____
1/4

8/12 - 3/12 = 5/12
solution :

8/12
-
3/12
_____
5/12

3/4 - 1/8 = 5/8
solution :

3/4 = 6/8
-
1/8 = 1/8
_____
5/8

* Unit Fractions : a fraction with a numerator of 1.

eg. 1/2, 1/3, 1/10, 1/100, 1/anything.

http://www.wisc-online.com/objects/ViewObject.aspx?ID=abm6007

Adding fractions with unlike denominators.

Adding fractions with unlike denominators.

Eg. 1/2 + 1/3 = 1 apple + 1 orange = 2 fruits

We must find a common denominator. - A multiple of the denominators of a set of fractions.

- Eg. a common denominator for 1/4 and 1/6 is 12 because common multiple of 4 and 6 is 12. 4 - 4, 8, (12), 16 6 - 6, (12), 18, 24

Eg. 1/2 + 1/3 = 3/6 + 2/6 = 5/6 <!--[if !vml]--><!--[endif]--> <!--[if !vml]--><!--[endif]-->

Homework: Math Links textbook pages 234-236 # 4-21 odd numbers. :)