If a small circle with a radius of 1 cm rolls once outside a large fixed circle with a radius of 4 cm, how many times does the small circle roll?
半径为1厘米的小圆在半径为4厘米的固定大圆外滚动一周，则小圆滚动了多少周．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>