Pave a road of 800 meters, 440 meters have been paved, how much is left unpaved.
铺一条800米的路，已经铺了440米，还剩多少没有铺．
<gadget id="calculator">800 - 440</gadget>
<output>360</output>

<gadget id="calculator">360 / 800</gadget>
<output>9/20 = around 0.45</output>

<result>9/20 = around 0.45</result>