If the radius of a circle is tripled, how does the circumference change?

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Answer 1 · 2015-11-23T17:34:20

The circumference is also trippled.

Let $r$ be the original radius.

Then the circumferrence is $C=2pir$

If we multiply the radius by $3$ then:

$r_1=3r$

$C_1=2pir_1=2pi*3r=3*2pir=3*C$

Answer 2 · 2015-11-23T17:35:12

The circumference of a cirlce with radius r is

$S=2*pi*r$

hence if the radius is tripled hence the new radius is $r'=3*r$

then the new circumference is $S'$

$S'=2*pi*r'=2*pi*(3*r)=3*(2*pi*r)=3*S$

Finally the circumference will be tripled.