Question

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

Answer 1

`\boxed {\boxed {\text{ Circumference of a circle = }2 \pi r}}`

Plug in the value of radius = 2.5 into the formula:

Circumference = 2π(2.5) = 15.71 ft (nearest hundredth)


Answer: 15.71 ft

Answer 2

Answer: The circumference of the circle is: " 16 ft. " ;
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or; " In term of
`\pi` , the circumference of the circle is: " 5
`\pi` ft. " .
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Step-by-step explanation:
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The formula for the circumference, "C" , of a circle:

→ " C = 2 *
`\pi` * r " ;

→ in which:

" C = circumference of the circle" ;

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


`\pi` = "3.14" ; which we can use as a commonly accepted
"approximated value" for "
`\pi`" ;

= "
`\pi` " ; 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 "
`\pi`" :

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

C = 2 *
`\pi` * r ;

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

→ C = 2 *
`\pi` * (2.5 ft) ;

= 2 * (2.5 ft) *
`\pi` ;

= 5
`\pi` ft.
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Answer: In terms of "
`\pi`" , the circumference of the circle is:

" 5
`\pi` ft. "
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Method 2) Solve for the circumference of the circle;

→ using "3.14" as an approximation for "
`\pi`" :
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Method 2) [A]:

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

Take the answer, which is: " 5
`\pi` ft" ;

And solve using "3.14" as an approximation for "
`\pi`" :

→ " 5 *
`\pi` " = " 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 "
`\pi`" :

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

C = 2 *
`\pi` * r ;

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

And substitute "3.14" as an "approximation for
`\pi`" ;
→ in place of the for "
`\pi`" 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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