What is the circumference of a circle with a radius of 2.5 feet

Answer:  The circumference of the circle is:  " 16 ft. " ;  
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or;  " In term of [tex] \pi [/tex] , the circumference of the circle is:  " 5[tex] \pi [/tex]  ft. " .
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Explanation:
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The formula for the circumference, "C" , of a circle:

→  " C = 2 * [tex] \pi [/tex] * r " ; 

→  in which:

      " C = circumference of the circle" ; 

       "r = radius ["length of radius"] = " 2.5 ft " (given) ; 

       [tex] \pi [/tex] = "3.14" ; which we can use as a commonly accepted 
                                              "approximated value" for "[tex] \pi [/tex]" ; 

                             =  "[tex] \pi [/tex] " ; or, we leave the symbol for "pi" as it is written; if 
                                                              we are to solve "in terms of pi" ; 
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Method 1)  To find the circumference, "C", of the circle; in term of "[tex] \pi [/tex]" :

Note the formula for the circumference, "C", of a circle:

C = 2 * [tex] \pi [/tex] * r ; 

Plug in our given value for the "radius, "r" ; (which is: "2.5 ft.

→  C  =  2 * [tex] \pi [/tex] * (2.5 ft) ; 

          =  2 * (2.5 ft) * [tex] \pi [/tex] ;

          =   5 [tex] \pi [/tex]   ft.
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Answer:  In terms of "[tex] \pi [/tex]" , the circumference of the circle is:  

                " 5 [tex] \pi [/tex]  ft. "
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Method 2)  Solve for the circumference of the circle;
 
→ using "3.14" as an approximation for "[tex] \pi [/tex]" :
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Method 2)  [A]: 

→  Start by solving for the circumference; "in terms of [tex] \pi [/tex]" ;
              →  {as done above} :

Take the answer, which is:  " 5 [tex] \pi [/tex]  ft" ;  

And solve using "3.14" as an approximation for "[tex] \pi [/tex]" :

→  " 5 * [tex] \pi [/tex] "  =  " 5 * (3.14) = 15.7 ft. ;

→  We can round to:  " 16 ft ." ← 2 significant figures.
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Method 2)  [B]:  To solve for the circumference of the circle;  
                    →  using "3.14" as an approximation for "[tex] \pi [/tex]" :

Note the formula for the circumference, "C", of a circle:

C = 2 * [tex] \pi [/tex] * r ; 

Plug in our given value for the "radius, "r" ; (which is: "2.5 ft.") ; 

And substitute "3.14" as an "approximation for [tex] \pi [/tex]" ;
                                                                   →  in place of the for "[tex] \pi [/tex]" symbol ;

And rewrite: 
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→  C  =  2 * 3.14 * (2.5 ft) ; 

↔  C  =  2 * (2.5 ft)  * (3.14) ;

           =  (5 ft) * (3.14) ;

           =  15.7 ft. ; we can round to:  " 16 ft."  (2 signifcant figures).

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