Question 333634
{{{C=2pi*r}}} Start with the circumference of a circle formula.



{{{C/(2pi)=r}}} Divide both sides by {{{2pi}}} to isolate "r".



{{{r=C/(2pi)}}} Flip the equation.



{{{r=42/(2pi)}}} Plug in {{{C=42}}}.



{{{r=42/(2*3.14159)}}} Replace {{{pi}}} with {{{3.14159}}} (note: Use more digits of {{{pi}}} to get better accuracy).



{{{r=42/(6.28318)}}} Multiply 2 and {{{3.14159}}} to get {{{6.28318}}}.



{{{r=6.68451325602641}}} Divide {{{42}}} into {{{6.28318}}} to get  {{{6.68451325602641}}} (this figure is approximate).



{{{r=6.685}}} Round to the nearest thousandth.



So the radius of a circle which has a circumference of {{{42}}} meters is about {{{6.685}}} meters.