March 14 is National Pi Day! No, not the PIE you eat. I'm talking about the mathematical constant, Pi, which is equal to approximately 3.14. 1
I wonder why Pi Day is on March 14? Here's a hint: Write March 14 with numbers. Pi = 3.14 2
Mathematicians say that Pi is approximately 3.14 because it's not exactly 3.14. Here's why: If you write Pi as a fraction, it's about. 22 7 3
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It goes on FOREVER... 5
What IS Pi, anyway? We use it to calculate the area of a circle. This is the symbol for Pi: This is the formula for Pi: Circumference= 3.14 x diameter or Circumference=22/7 x diameter C= 3.14d When just the radius is given, you must double the radius and then, multiply that number by Pi (3.14 or 22/7) C=2r x 3.14 or 2r x 22/7 6
Pi is always the same, no matter how big or how small the circle. That is why mathematicians call it a constant. A brief history of Pi It's been known for 4,000 years. Ancient cultures used a form of Pi for calculating the area of circles. Babylonians, Egyptians Archimedes of Syracuse was the first to calculate Pi (287 212 BC) Mathematicians began using the Greek symbol in the 1700's. 7
Is it REALLY a "constant"? How can it be the same no matter how big or small the circle is? Let's investigate! Watch your teacher demonstrate. You will try this next with your own circular object. 8
Cutting π Materials circular object string scissors tape To Do and Notice Carefully wrap string around the circumference of your circular object. (Ask a partner to help.) Cut the string when it is exactly the same length as the circumference. Now take your string circumference and stretch it across the diameter of your circular object. Cut as many string diameters from your string circumference as you can. How many diameters could you cut? Compare your data with others. What do you notice? What s Going On? This is a hands on way to divide a circle s circumference by its diameter. No matter what circle you use, you ll be able to cut 3 complete diameters and have a small bit of string left over. Estimate what fraction of the diameter this small piece could be (about 1/7). You have cut pi, about 3 and 1/7 pieces of string, by determining how many diameters can be cut from the circumference. Tape the 3 + pieces of string onto paper and explain their significance. 9
Click the picture to take you to a "Pi Day Rap." You will need to click on this picture again once you reach the webpage. 10
Let's eat pie! Remember your manners: Be patient; wait for your turn. Eat politely; chew with your mouth closed. Throw away your trash. Class Assignment: p. 493 #1 5 Remember, you multiply 3.14 x the diameter. If they only give you the radius, you double that to find the diameter. 11
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p. 493 #1 5 Remember, you multiply 3.14 x the diameter. If they only give you the radius, you double that to find the diameter. 13
Other teacher ideas: Pi Chain (General) Create the longest Pi Chain ever! We have a NEW CHAMP! The students in Madison Junior High, Madison, NJ set a new "world" record of 2,201 digits!!! Their teacher Ms. Prill wrote in very proudly. Great job to those students at Madison Junior High! Well, this certainly gives us something to strive for. In 2000, the students in Williamstown Middle School (NJ) created one 1846 links long as it wrapped its way through the hallway! Make up a color scheme 10 colors one for each number. Example: 0 is green, 1 is yellow, 2 is blue, etc Around Town... (Elementary Middle) I got this idea while driving... Students are given 2 minutes to write down as many things as they can think of that are circles. CD's, Buttons, coins, etc. Winner is the student with the most. This contest could also be run like "Boggle" where you throw out any item that any other student thought of and crown the winner as the student with the most original items. 14
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Solid Figures Surface Area= the sum of the areas of the faces. Rectangular Prisms To find the surface area, find the area of each face, then add all of the faces together. See the example on p. 495; they used a chart to keep track of each face's measurements. 16
Surface Area of a Rectangular Prism top Face Length Width Area bottom front back left side right side sum: 17
Cubes To find the Surface Area of a Cube, find the area of one side of the cube, then multiply that number by 6. See the example on p. 495. 18
Volume Volume of a solid figure is a measure of the amount of space the figure occupies. To find the volume of a rectangular prism, multiply the length times the width times the height. V= l x w x h To find the volume of a cube, use this formula: V= s 3 V= side x side x side 19
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