30 identical trapezoids should be cut out from a sheet of iron. The upper base of the trapezoid is 4 cm, the lower base is 6 cm, and the height is 5 cm. What is the minimum square centimeter of this iron sheet?
要从一张铁皮上剪出30个同样的梯形，梯形的上底是4厘米，下底是6厘米，高是5厘米．这张铁皮至少是多少平方厘米？
<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">10 * (5/2) * 30</gadget>
<output>750</output>

<result>750</result>