A sidewalk is 20m long and 1.5m wide. If you want to lay a trapezoidal brick with an upper base of 10 cm, a lower base of 20 cm, and a height of 5 cm on this sidewalk, how many such bricks are needed?
一条人行道长20m，宽1.5m．如果要在这条人行道上铺上一种上底10cm，下底20cm，高5cm的梯形砖，需要多少块这样的砖？
<gadget id="calculator">10 + 20</gadget>
<output>30</output>

<gadget id="calculator">5 / 2 / 10_000</gadget>
<output>1/4_000 = around 0.00025</output>

<gadget id="calculator">30 * (1/4_000)</gadget>
<output>3/400 = around 0.0075</output>

<gadget id="calculator">1.5 / (3/400)</gadget>
<output>200</output>

<gadget id="calculator">20 * 200</gadget>
<output>4_000</output>

<result>4_000</result>