How many circles with a radius of 2.5 decimeters can be cut from a rectangular piece of paper with a length of 30 decimeters and a width of 15 decimeters?
从一张长30分米、宽15分米的长方形纸中，最多能剪出多少个半径是2.5分米的圆．
<gadget id="calculator">2.5 * 2</gadget>
<output>5</output>

<gadget id="calculator">30 / 5</gadget>
<output>6</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<result>18</result>