A good answer might be:

There are many interesting ways to fill in the blank. My choice is:

int count = 1;
while ( count <= 10 )
{
  circ.setRadius( (100/10)*count );
  circ.draw(gr);
  count = count + 1;
}

Since the width (and height) of the drawing area is 200, circles can have a radius of up to 100. For ten circles, that maximum radius is divided by ten to give the size increase in each radius.