Master Wang cut the largest square from a rectangular plank with a length of 50 decimeters and a width of 30 decimeters. How many square meters are left on this plank?
王师傅从长50分米、宽30分米的长方形木板上，裁下一个最大的正方形．这块木板还剩下多少平方米？
<gadget id="calculator">50 / 10</gadget>
<output>5</output>

<gadget id="calculator">30 / 10</gadget>
<output>3</output>

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

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">15 - 9</gadget>
<output>6</output>

<result>6</result>