1. Discovering
Area of a
Circle

2. Area of a Circle Discovery
For Learning to Happen:
Pay close attention to this lesson.
Listen to my instructions to discover the area of a circle formula.

3. Area of a Circle Discovery
You are going to get a white half sheet.
Label the circumference, diameter and radius on your circle.

4. Area of a Circle Discovery
Circumference
Diameter
Radius
Carefully cut out the circle on the black line.

5. Area of a Circle Discovery
Cut out the circle on the bolded lines.
Cut along the diameter to cut the circle in half.
You should have 2 halves.

6. Area of a Circle Discovery
Start from the diameter and cut the 4 pieces.
DO NOT CUT IT TO THE EDGE!
Open the semicircles and bend them out so they look like 4 connected triangles.

7. Area of a Circle Discovery
Fit the 4 triangles together so that as one is facing up, the other is facing down.
Tape these pieces together on your blue study guide handout.
Make sure your words on facing up!
radius
Circumference

8. Area of a Circle Discovery
Answer the following questions.
What does your new figure look like?
Parallelogram
2a. Draw your answer here. Label base & height
2b. How do you find the area of a parallelogram?
Base x Height
height
base

9. Area of a Circle Discovery
3. Draw your area of a circle figure below. In knowing that you need to find the base and height of your new figure to calculate the area, what is the height of your new figure? Label your picture.
4. What is the bottom base of your new figure? Label your picture above. Hint: Half of the circumference.
Height = radius
pi x radius

10. Area of a Circle Discovery
If you know the base and height of your new figure can you find the area? Take your base and multiply it by your height. Show your work!
6. Simplify your formula.
7. Write out how you find the area of a circle.
Pi times radius squared.

11. Area of a Circle Discovery
Here is what we just did:
We labeled everything.
Area = base times
the height. r r
radius
Circumference is
the distance
around the circle.
We cut our circle
in half making two
pieces.

12. Area of a Circle Discovery
Watch what happens when we use a circle with 16 triangles instead of using a circle with 8 triangles. r r
Notice that with more triangles the figure begins to really resemble a parallelogram. Area of a parallelogram is base times height.

13. Area of a Circle Discovery
Take out a calculator to try to solve the following problems on area of a circle.

14. Area of a Circle Discovery
6 in.
Find the area of the circle.

15. Area of a Circle Discovery
11 m.
Find the area of the circle.

16. Find the area of the circle.
Area of a Circle Discovery
What is the radius if the diameter is 10 ft?
10 ft.
Find the area of the circle.

17. Take out your study guide!
Area of a Circle Discovery
That's all Folks!
The End!
Take out your study guide!
That’s all folks

18. copyright©amberpasillas2010
Area of a Circle #7
6 in
= 3.14 or 22 7
copyright©amberpasillas2010

19. Given the Radius of a Circle#8
Given the Radius of a Circle
Round to the nearest hundredths place and include units!
5 ft
Find the Circumference
Find the Area
copyright©amberpasillas2010

21. Use this as a master to give to students
for the interactive discovery of a circle along with a copy of the worksheet.
Student materials for interactive discovery of a circle: Copy of circle pictured above, copy of area worksheet in this folder, scissors & tape.

22. Area of a Circle Area of a Circle
Follow the teacher directions and cut the circle out.
Area of a Circle
Follow the teacher directions and cut the circle out.

23. TEACHER NOTE: Give each student a copy of this page
TEACHER NOTE: Give each student a copy of this page. The master copy is in the folder as a pdf.

24. http://www.mathslideshows.com Hello!
Thank you for downloading my Math Slideshow Powerpoint. I have over 175 animated Math Slideshows, 225 Math Warm Ups, Study Guides, Worksheets, and much more available on my website at
I have attached the list below so you can see what is available. If you teach 5th-10th grade this is the place for you! Please check it out!
Sincerely,
Amber Pasillas

25. Math PowerPoint Slideshows Available
AREA FORMULAS $30
1. Area of a Rectangle & Square
2. Area of a Parallelogram & Triangle
3. Area of a Trapezoid
4. Area of a Circle Discovery WS
5. Area of Irregular Figures
6. Area of Composite Figures
7. Perimeter & Area Review
DECIMALS $30
1. Rounding Decimals
2. Add and Subtract Decimals
3. Add & Subtract Negative Decimals
4. Multiply Decimals
5. Divide Decimals
6. Multiply & Divide Negative Decimals
7. Decimal Place Value, Perimeter & Area
EQUATIONS $50
1. Equation Introduction
2. Add & Subtract One Step Equations
3. Multiply & Divide One Step Equations
4. Integers and Equations WS
5. Solve 2 Step Equations Using Algebra Tiles WS
6. Solve 2 Step Equations WS
7. Multi-Step Equations Combine Terms Day 1
8. Multi-Step Equations Translate Day 2 WS
9. Negative Coefficient Equations
10. Variables On Both Sides Equations Algebra Tiles WS
11. Distributive Property Equations WS
12. Equations Review
EXPONENTS & POWERS $30
1. Exponents Introduction
2. Zero and Negative Exponents
3. Fractions with Negative Exponents
4. Multiplying Exponents
5. Factoring, Fraction Exponents
6. Divide Powers, Multiply & Divide Monomials
7. Exponent Review
EXPRESSIONS $20
1. Evaluate Algebraic Expressions
2. Writing Algebraic Expressions
3. Combing Like Terms Algebra Tiles WS
4. Combine Terms & Properties Review
5. Terms, Evaluate, Perimeter & Area
FORMULAS $15
1. Perimeter, Area, & Distance Formulas
2. Commission, Sales Tax & Leaving a Tip
3. Unit Analysis, Convert Units, Mass Formula
4. Simple Interest

26. Math PowerPoint Slideshows Available
FRACTIONS $50
1. Equivalent Fractions, Simplest Form, Giant One
2. Mixed Numbers & Improper Fractions
3. LCD, Comparing Fractions
4. Fraction Review (Equivalent, Mixed, Compare)
5. Add & Subtract Fractions Same Denominator
6. Add & Subtract Fraction MODEL WS
7. Add & Subtract Unlike Denominators
8. Add, Subtract, & Multiply Mixed Numbers
9. Multiply Fraction MODEL WS
10. Multiply Mixed Numbers
11. Reciprocals
12. Divide Fractions
13. Fraction Review
14. Add & Subtract Negative Fraction Unlike Denomin.
15. Add & Subtract Negative Fraction MODEL
FRACTION, DECIMAL & PERCENT $20
1. Fractions as Decimals, Terminating & Repeating
2. Decimal Patterns, Repeating Decimals as Fractions WS
3. Percents to Decimals & Fractions
4. Fractions & Decimals to Percents
5. Fractions, Decimals & Percents Review WS
6. Fractions & Decimals & Percents
GRAPHING & FUNCTIONS $50
1. Graphing in a Coordinate Plane
2. Is The Ordered Pair a Solution? WS
3. Function Form WS
4. Mystery Graph & Silent Board Game WS
5. Graphing Equations & Parabolas WS
6. x and y intercepts
7. Slope of a Line Day 1
8. Slope of a Line Day 2
9. Graphing Slope Review
10. Graphing Shortcut
11. y = mx + b WS
GUESS & CHECK TABLES $20
1. Guess & Check Tables 1 WS
2. Guess & Check Tables 2 WS
3. Guess & Check Tables 3 WS
4. Guess & Check Tables Review WS
5. Guess & Check Perimeter & Area WS
HOLIDAY MATH $10
1. Halloween Math WS
2. Thanksgiving Math WS
3. December Math WS

27. Math PowerPoint Slideshows Available
INEQUALITIES $25
1. Inequalities Introduction
2. Inequalities Add & Subtract WS
3. Positive Inequalities Multiply & Divide WS
4. Negative Inequalities WS
5. Two Step Inequalities
6. Inequality Review WS
INTEGERS $50
1. Integers & Absolute Value Introduction
2. Add Integers Hands On MODEL
3. Add Integers With a Number Line
4. Subtract Integers Hands on MODEL WS
5. Subtract Integers Review
6. Subtract Integers With a Number Line
7. Slider Game Integer Review WS
8. Multiply Integers Day 1 WS
9. Multiply Integers Day 2
10. Divide Integers
11. Integer Review
MATH ART & GAMES $30
1. Bingo Game WS
2. Optical Illusions
3. Tessellations, MC Escher
4. Game of Poison
5. Game of Mancala
6. Line Designs
7. Networks, Leohnard Euler
8. Beauty of Math, Last Day of School
MULTIPLICATION $10
1. Area Multiplication 1 WS
2. Area Multiplication 2 WS
3. Lattice Multiplication
NUMBER SYSTEMS $10
1. Compare and Order Rational Numbers
2. The Real Number System
3. Rational Numbers
4. Rational Number Game WS
NUMBER THEORY $20
1. Divisibility Rules
2. Prime Numbers Discovery: Eratosthenes
3. Prime Factorization, Make a List
4. Greatest Common Factor
5. Least Common Multiple
PERCENT $30
1. Percent Shortcuts WS
2. Percent Problems, solve for %
3. Percent Problems (part/whole, is/of) WS
4. Percent of a Number
5. Percent of Increase or Decrease
6. Percent of Markup or Discount
7. Commission, Sales Tax & Leaving a Tip
8. Percent & Discount Review WS

28. Math PowerPoint Slideshows Available
PERIMETER & CIRCUMFERENCE $15
1. Perimeter of Polygons
2. Circumference of a Circle Discovery WS
3. Circumference of a Circle Review
4. Perimeter & Area Review
POINTS, LINES, PLANES & ANGLES $20
1. Points, Lines & Planes
2. Angles: Acute, Right, Supplementary, Com.
3. Measuring Angles With a Protractor
4. Parallel, Perpendicular & Skew Lines
5. Angles: Adjacent & Vertical, Transversal
POLYGONS & CIRCLES $15
1. Classifying Triangles: Acute, Right & Obtuse
2. Quadrilaterals Introduction
3. Circles Introduction
4. Congruent Polygons
PROBABILITY $15
1. Probability Introduction
2. Experimental Probability: Coin Toss WS
3. Probability: Roll & Add Two Dice WS
4. Probability Game: Rock, Paper & Scissors WS
5. Probability of Compound Events
PROBLEM SOLVING $5
1. Problem Solving
2. Problem Solving Strategies
PROPERTIES $25
1. Order of Operations 1
2. Order of Operations 2
3. Commutative, Associative & Identity Properties
4. Distributive Property Generic Rectangles WS
5. Combine Terms & Properties Review
6. Equations & Inverse Property
RATIOS & PROPORTTIONS $30
1. Ratio, Rates & Unit Rate
2. Unit Rate & Unit Price
3. Writing Proportions
4. Dimensional Analysis Converting Units
5. Proportions Review
6. Similar Figures
7. Indirect Measurement
8. Unit Rate, Unit Analysis, Missing Units
9. Scale Drawings
SCIENTIFIC NOTATION $5
1. Scientific Notation Day 1
2. Scientific Notation Day 2 
SQUARES, SQUARE ROOT, PYTHAGOREAN $20
1. Square and Square Root
2. Estimating Square Roots
3. Discover Pythagorean Theorem WS
4. Pythagorean Theorem Day 2
5. Converse of Pythagorean Theorem

29. Math PowerPoint Slideshows Available
SURFACE AREA & VOLUME $50
1. Three Dimensional Figures
2. Volume of a Prism
3. Volume of a Cylinder WS
4. Volume of a Pyramid or Cone
5. Make a Net of a Rectangular Prism WS
6. Surface Area of Prisms Day 1
7. Surface Area of Prisms Day 2
8. Surface Area of a Square Pyramid
9. Surface Area and Volume of a Sphere
10. Surface Area and Volume Review
11. Formulas You Need To Know WS
TYPES OF GRAPHS $20
1. Stem & Leaf and Line Plots
2. Calculating The Mean
3. Mean, Median, Mode, & Range
4. Box and Whisker Plots
5. Scatter Plots and Correlation
CREATED BY: Amber Pasillas
TO ORDER:
PHONE: (530)
BEST DEAL
All math slideshow lessons
listed above & worksheets. =
$300
If your slideshow has blank boxes in it, you need to download MathType software. It allows you to see all math formulas correctly. This software is similar to equation editor and is available for free at
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