The upper base of a trapezoid is 5cm, the lower base is 100m, and the height is 4cm. What is its area in square centimetres?
一个梯形的上底是5cm，下底是100m，高是4cm，它的面积是多少平方厘米．
<gadget id="calculator">100 * 100</gadget>
<output>10_000</output>

<gadget id="calculator">5 + 10_000</gadget>
<output>10_005</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">10_005 * 2</gadget>
<output>20_010</output>

<result>20_010</result>