There is a piece of triangular glass with a base length of 40dm and a height of 20dm. If the glass costs 30 yuan per square meter, how much does it cost to buy such a piece of glass?
有一块三角形的玻璃，底边长40dm，高是20dm，如果每平方米玻璃30元，买这样一块玻璃需要多少元？
<gadget id="calculator">20 / 2 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">40 * (1/10) * 30</gadget>
<output>120</output>

<result>120</result>