Question 705341
The speed of the model plane is {{{ 175 }}} units/sec
This is distance around, or  along the circumference.
In {{{ 1 }}} sec, it travels {{{ 175*1 = 175 }}} units
In {{{ 3 }}} sec, it travels {{{ 175*3 = 525 }}} units
-----------
Now I can say
{{{ C = 525 }}}
{{{ C = 2*pi*r }}}
{{{ 525 = 2*pi*r }}}
{{{ r = 525 / ( 2*pi ) }}}
{{{ r = 83.556 }}} units