The blades of a breeze ceiling fan are composed of three trapezoidal plastic sheets. It is known that the upper bottom of each plastic sheet is 3 cm, the lower bottom is 4 cm, and the height is 10 cm. The three blades of this ceiling fan need plastic in total. How many square centimeters is the piece?
一种微风吊扇的叶片是由三块梯形形状的塑料片组成的，已知每块塑料片上底是3厘米，下底是4厘米，高是10厘米，做这个吊扇的三块叶片共需塑料片多少平方厘米？
<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">7 * 5</gadget>
<output>35</output>

<gadget id="calculator">35 * 3</gadget>
<output>105</output>

<result>105</result>