Wednesday, June 19, 2019

What is pi?    

 It's not just a Greek letter. 
Did you know that no matter what size the CIRCLE:

If you divide its Circumference by it's diameter

 you will get pi (3.14),  

 o     O  o     O       

Well how do you find the  CIRCUMFERENCE (C) of a CIRCLE?               (distance around)

       And how do you find the DIAMETER (d)  OF A CIRCLE?                       (distance across)

O

1. fIRST FIND THE DIAMETER:  You need a ruler, and a Circle.  Measure straight across the center of the circle:  that's the diameter


2..  SECOND USE THE CIRCUMFERENCE formula (it works, trust me).


        Circumference = diameter * pi    (C = d * pi)

 Well what is pi?    You tell me!!                                                      (I'm confused)

(pi = 3.14)                                                          IF                                                             

  C = d * pi     [Algebra]  THEN   pi = C/d  (you divided both sides by d)

                             

Try it!!   

     Start Here:
               Measuring across a circle with a ruler-- you get 10 centimeters.     (diameter)
        
                If  you GOOGLE  "pi"    you get  3.1415...
         WE JUST USE  3.14 = pi        OK?


   diameter = 10 centimeters (cm)   and pi = 3.14

C = d* pi
Circumference = diameter * pi

C = 10 cm * 3.14  (do the math)

10 cm * 3.14  =   31.4 cm

     
SO THIS CIRCLE HAS A CIRCUMFERENCE OF 31.4 centimeters (cm)?
YES

 (Why?    because... you need to go back and find out)
          NOW THE FUN STUFF:    
                                     
pi  =  Circumference
                                             diameter                       (YES! see above)

       Three CIRCLES: 

#1. circumference is 6.28 cm  and diameter is  2 cm
                   

               6.28 cm/2cm  = 3.14
 

 
#2. circumference is 18.6 cm  and diameter is   6 cm
                    


                 18.6 cm  = 3.14    
6 cm
   
#3. circumference is  15.5 cm   and diameter is  5 cm
  

                  15.5 cm   = 3.14
   5 cm


 ITS A CIRCLE: 
C = d * pi                   C / d = pi
     
      So, who cares?   Well, this is where they got pi. And it works for any circle.   Pi is called a ratio because ratio means divide and you divide Circumference of a circle by its diameter to get pi.                                
  Image result for circumference formula clipart
                    Voila!     A Ratio         (...and remember, a fraction is just a division problem...)