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.