Students use red paper to make right-angled triangle flags, each with a base of 20 cm and a height of 1 decimeter. How many square decimeters of red paper is needed to make 20 small flags like this?
同学们用红纸做直角三角形小旗，每面小旗底是20厘米，高是1分米．做20面这样的小旗，至少需红纸多少平方分米？
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">20 * 1 * 5 * (1/5)</gadget>
<output>20</output>

<result>20</result>